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Saturday 27 June 2015

Air Conditioner Compressor Failure

How To Diagnose an a/c Compressor Failure and Prevent It From Happening Again

Adapted from an article written by Larry Carley for Import Car magazine

The compressor is the heart of the refrigeration circuit. It pumps and pressurizes the refrigerant to move it through the A/C system. Compressors work hard and run hot, up to several hundred degrees and several hundred pounds per square inch of internal pressure. They rely on only a few ounces of lubricant to keep their parts moving. If the lubricant is lost because of a leak, or the lubricant breaks down due to contamination, the compressor will not last. Sooner or later, the compressor will call it quits.

The most common symptom of a compressor failure (besides no cooling) is a seized compressor. It will not turn when the magnetic clutch engages, and you may hear squeals of protest from the drive belt. Or, the belt may have already broken or been thrown off its pulleys.

Loss of lubrication is unquestionably the most common cause of compressor failure. This can happen when there is a refrigerant leak somewhere in the system that allows refrigerant and oil to escape. Typical leak points are hoses, hose and pipe connections (O-rings and flange gaskets), the evaporator, condenser or the compressor shaft seal. An electronic leak detector or dye should be used to find the leak so it can be repaired.

A restriction inside the A/C system can also starve the compressor for oil. Oil circulates with the refrigerant, so if the orifice tube or expansion valve is blocked it may cause the compressor to run dry and seize.

Even if a compressor is still turning, it may have to be replaced if it is leaking, making excessive noise or not working correctly. Some compressors are naturally noisier than others, but loud knocking noises can sometimes be caused by air in the system (the cure here is to vacuum purge the system to remove the unwanted air, then to recharge the system with refrigerant). Metallic noises and bearing noise are usually signals that the compressor is about to fail.

A new compressor may be needed if the unit is leaking internally or not producing enough pressure due to bad reed valves, worn piston rings, or worn or scored cylinders, etc.). A worn compressor or one with internal problems will not be able to develop normal operating pressures with a full charge of refrigerant. This kind of problem can be diagnosed with an A/C gauge set.

Poor cooling can also be caused by a lot of things other than a bad compressor, so do not replace the compressor until you have ruled out other possibilities such as a low refrigerant charge, too much oil in the system, air contamination, a clogged condenser, plugged orifice tube, inoperative electric cooling fan, etc.

Compressor operation can be affected by sensors in vehicles with automatic temperature control systems. Some have an A/C pressure transducer (usually mounted in the high side line) to monitor refrigerant pressure and shut off the compressor if pressure gets too high; a compressor temperature sensor to turn off the compressor if it gets too hot; and/or a compressor rpm sensor to monitor belt slippage. Mitsubishi, for example, uses a "belt lock controller" to disengage the compressor if the drive belt slips or the compressor seizes.

On 1996 and newer Mercedes-Benz E-Class cars, the A/C control module will disengage the compressor if the refrigerant temperature and pressure sensors do not show a rise when the compressor is being driven.

COMPRESSOR CLUTCH PROBLEMSIf the compressor is not turning, make sure the magnetic clutch engages when energized. Underlying problems here may include a bad relay, fuse, wiring problem or a defective clutch. If the clutch fails to cycle on and off when the A/C is turned on, jumping the clutch lead with a jumper wire from the battery will show if the problem is in the clutch or elsewhere. If the clutch engages, the problem is the clutch power supply (relay, fuse, wiring, switch or control module). Refer to a wiring diagram and work backward toward the battery to find out why the voltage is not getting through.

Many A/C systems have a low-pressure cutout switch that prevents the compressor clutch from engaging if system pressure (the refrigerant charge) is too low. This is designed to protect the compressor from damage in the event of a leak. So if the clutch is not engaging, check the refrigerant charge and the cutout switch. The clutch air gap is also important for proper clutch operation. If the clearance is not correct, the clutch may slip and burn or not engage at all. The specs can be found in a service manual along with adjustment procedures. Generally speaking, most clutches call for a 0.015 to 0.040 inch press fit clearance.

DEFECTIVE COMPRESSORS?How often do compressors fail as a result of "manufacturing defects?" Not very often. According to one compressor manufacturer who examined 75 compressors that had failed and were returned under warranty, only two were found to have manufacturing defects. The rest failed because of problems such as too little oil in the system, air in the system, contaminants in the system, or "installer error." The latter category included using the wrong type of compressor lubricant, not using enough lubricant, using non-approved flushes to "clean" system parts, and using cross-contaminated refrigerants. Debris left over from a previous compressor failure was the most common cause of repeat compressor failures.

Always use the type of lubricant recommended for specific compressors. This is especially important with rotary vane and scroll-type compressors. A replacement compressor may or may not contain lubricant from the factory. In some cases, the shipping oil must be drained before the compressor is installed. In other cases, the compressor may contain a POE or a PAG oil lubricant that may or may not be compatible with the vehicle requirements. Follow the compressor suppliers installation instructions to the letter to avoid warranty problems later on.

Before adding fresh oil to a system, all the old oil should first be removed. This will prevent cross-contamination of lubricants and reduce the risk of overcharging the system with too much oil (which can cause cooling problems). Always refer to the OEM oil capacity chart for the vehicle application. The following is a list of recommended lubricants for R-134a import compressors:

Behr/Bosch rotary compressors - Ester 100;
Behr/Bosch piston compressors - PAG 46;
Calsonic V5 - PAG 150;
Calsonic V6 - PAG 46;
Diesel/Kiki (Zexel) DKS, DKV & DCW - PAG 46;
Hitachi (all) - PAG 46;
Keihin (all) - PAG 46;
Matsushita (all) - Ester 100;
Mitsubishi FX80 - PAG 100;
Mitsubishi FX105 - PAG 46;
Nihon (all) - Ester 100;
Nippondenso 6P, 10P, 10PA, 10P08E - PAG 46;
Nippondenso SP127, SP134 & 6E171 - PAG 46;
Nippondenso TV series - PAG 125;
Panasonic (all) - PAG 46;
Sanden SD500 & SD700 - PAG 100;
Sanden SD710, SDB, TV & TRS - PAG 46; and
Seik-Seiki (all) - Ester 100.

FLUSHING AFTER A COMPRESSOR FAILUREWhen a compressor fails, it may spit metallic debris into the A/C system. Most of this debris ends up in the condenser where it can block tubes and interfere with efficient cooling. Some of the debris may be carried to the orifice tube or expansion valve and create a blockage. Debris can even be blown back into the suction tube. If not removed by flushing, it can be sucked back into a new compressor and cause it to fail.

Flushing the hoses is always recommended following a compressor failure. Flushing the condenser is also recommended. But with many condensers, replacement is the only sure-fire way to get rid of contaminants. Older serpentine-style tube-and-fin condensers can often be flushed successfully, but parallel flow condensers are very difficult to clean. So too are newer style condensers with extremely small extruded tubes. For these kinds of applications, the condenser should be replaced. It is expensive, but not as expensive as ruining a new compressor because of residual debris or sludge in the old condenser.

After flushing, install an in-line filter after the condenser to trap any debris that might still be inside. The filter will prevent anything that works loose from being carried to the orifice tube.

You should also install a filter screen in the suction hose at the compressor inlet to protect the new compressor from any debris that might be upstream inside the suction hose or evaporator.

Another reason for flushing is to remove residual oil from the system. This is necessary when retrofitting an older R-12 system to the new ozone-safe R-134a refrigerant, but it is also a good way to make sure the system contains the right amount of oil. Simply adding oil to the system to replace that which has been lost is a guess at best, because there is no way to know how much has been lost due to leakage. Estimating a couple of ounces here and there for replacing an accumulator, receiver/drier, condenser, compressor or hoses is not a very accurate means of determining how much oil needs to be added to the system when it is recharged with refrigerant. Flushing gets rid of all the oil so the exact amount specified by the vehicle manufacturer can be added back to the system.

What happens if there is too little or too much compressor oil in the system? Not enough oil in the system will reduce compressor lubrication and may lead to premature failure. Too much oil in the system can puddle in the condenser and obstruct the flow of refrigerant causing a drop in cooling performance.

Other parts that should also be replaced following a compressor failure include the accumulator or receiver/dryer, and the orifice tube or expansion valve. The former contains a bag of desiccant that traps moisture and acts as a filter to protect the system. A new orifice tube or expansion valve is recommended because the small hole in this metering device can become easily plugged with debris. An aftermarket "variable orifice tube" can improve low-speed cooling.

EVACUATING & RECHARGING THE AIR CONDITIONING SYSTEMAfter the compressor has been installed and the hoses are reconnected, the A/C system must be thoroughly evacuated with a vacuum pump to pull out air and moisture. If not purged from the system, air will reduce cooling efficiency. Moisture will react with refrigerant oil and produce acids and sludge. Moisture can also freeze and plug the expansion valve causing noise, restrictions or a complete blockage.

A pump capable of achieving high vacuum must be used to pull out all of the contaminants. When air is pulled out of the system, it creates a vacuum that causes residual moisture to boil and evaporate. For this to occur, the vacuum pump must be capable of pulling at least 29 in. Hg of vacuum throughout the evacuation process (which normally takes about 30 minutes).

One of the best ways to monitor the evacuation process is with a Thermistor Vacuum Gauge that reads in microns (one inch of Mercury equals 25,400 microns). It takes a highly accurate instrument to measure vacuum because even a little pressure left in the system can prevent all the residual moisture from boiling out. Only a 1/2 inch of mercury of pressure (12,700 microns) can reduce the boiling point of water by more than 20 degrees F. Pulling out the last fraction of an inch of pressure is the most critical step in the evacuation process to ensure complete removal of all air and moisture.

After pulling a deep vacuum on an A/C system, close all valves and shut off the vacuum pump. A slow rise in pressure (which you can see on the Thermistor Vacuum Gauge) will occur as the residual moisture continues to boil off inside the system. Pulling additional vacuum will get rid of this moisture. The evacuation will not be complete until the system can maintain a stable vacuum reading below 700 microns for at least three minutes.

The time it takes to completely evacuate an A/C system can be reduced by preconditioning the evaporator prior to hooking up the vacuum pump. Preconditioning raises the temperature so the moisture will boil off faster. The easiest way to raise the temperature of the evaporator is to run the engine with the heater on HOT in the RECIRC mode. Turn the blower fan to HI and close all doors and windows. When the engine reaches normal operating temperature, the evaporator will be thoroughly preheated and ready to evacuate.

If you have difficulty maintaining a stable deep vacuum, there may be a leak in the A/C system, the vacuum pump or the equipment connections. Leak testing should be done prior to evacuating the system because evacuation is not always a reliable way to locate or even identify a small leak in an A/C system. Seals and O-rings that leak under pressure may move under evacuation and not leak.

Finally, recharge the system with the recommended amount of refrigerant and compressor oil. Do not overcharge and do not add too much oil. Check cooling performance to verify that everything is working properly and that the new compressor is doing its job.

GM Analysis of Compressor Failures

A recently completed analysis of air conditioning compressors in General Motors vehicles that had been replaced for noise, vibration and insufficient cooling concerns has indicated a high number of no trouble found results. Further studies have shown that the root cause of the customer concerns that might lead to a compressor replacement was often a state of refrigerant charge issue or in another area or system of the vehicle.
The A/C system refrigerant charge level, either high or low, has been found to be a major contributor to unnecessary compressor replacement. The ability of a refrigerant recycling/recharging tool to recover and measure the weight of the A/C system refrigerant charge will help the technician make a more accurate diagnosis of a charge level concern prior to any component replacement.
A thorough visual inspection should always be performed before any tests or repairs are done. Doing so may find an obvious problem that will save time and eliminate the need for extensive diagnosis. Some additional items, as listed below, should be considered before a compressor is replaced for noise, vibration or insufficient cooling concerns.
The compressor mounting bolts, brackets or braces may be loose or missing.
The compressor drive belt may be frayed, loose or misaligned.
The A/C refrigerant lines may be grounding out on body, chassis or engine components. This may allow noise and vibration to be transmitted into the passenger compartment.
The air flow through the condenser may be insufficient.
The condenser fins may be bent or filled with debris, or the space between the condenser and radiator may be filled with leaves or debris, or the cooling fans may be inoperative or not performing as designed, or the installation of aftermarket accessories may alter or restrict the air flow through the condenser.
Inspect for missing or mispositioned air deflectors, baffles, seals and shrouds.
The compressor cycling switch may not be operating correctly. This may allow the evaporator core to freeze up or the compressor may not stay engaged long enough for proper system pressures to develop.
The air flow through the evaporator core may be restricted.
The cabin filter may be plugged, or the evaporator core may be covered with debris, or the cowl air inlet leaf screen may by plugged.
The A/C system may be overcharged or undercharged with refrigerant. The A/C system charge weight can be measured with the RRR tool after a refrigerant recovery is done.
The A/C system may have an improper amount or incorrect type of refrigerant oil.
An A/C system sealer is not approved for use in GM vehicles.
The refrigerant may be contaminated or contain an excessive amount of air. The A/C system may have been charged with an unapproved refrigerant. The refrigerant identifier on the ACR 2000 should alert the technician to these conditions.
The orifice tube or thermostatic expansion valve (TXV) may be restricted, plugged or inoperative.
The capillary bulb on the TXV must be properly positioned so that the valve will provide proper refrigerant flow.
The desiccant bag in the accumulator may have failed, allowing debris to circulate in the A/C system.
The A/C system charge weight may have been changed. Components with an updated design may have been released. A check for service bulletins applicable to the vehicle being worked on should always be done.
A check for diagnostic trouble codes in all the control modules on the vehicle should be done. Some trouble codes will disable compressor operation after they have set. They must be repaired and cleared before compressor operation is allowed.
Verify that the engine is not operating with a low unstable idle, and that the engine is operating within the compressor engagement parameters (for example, the engine may be overheating or it may be too cold for compressor engagement).
The diagnostic procedures in the HVAC section of the service manual should be performed as written to prevent the misdiagnosis of a customer concern. The HVAC Diagnostic System Check and the A/C System Performance Test are written for a specific model only. They are not generic charts. They follow a logical order with detailed instructions on how to perform each step.
When a thorough HVAC system diagnosis indicates that the compressor should be replaced, follow the procedure in the appropriate service manual. The oil balance instructions are an important part of the replacement procedure. The correct refrigerant oil, as listed in the service manual, must be used in the new compressor. It is recommended that a suction screen filter be installed on Delphi Harrison compressors that do not already have one. The suction screen filter is not approved for use on compressors from other manufacturers. Refer to Corporate Bulletin Number 01-01-39-003A for more information on A/C suction screen kit repair recommendations and procedures. If the compressor has had a catastrophic internal failure, an inline filter may be required to capture the large amount of debris that may be found to be circulating in the A/C system. In addition, the A/C system may require flushing. Refer to Corporate Bulletin Number 01-01-38-006B for more information on flushing procedures and recommendations.
The addition of fluorescent refrigerant leak dye to the A/C system is recommended if the vehicle does not have it installed already. Some vehicles have leak dye installed at the assembly plant and this will be indicated on the A/C charge label. Refer to Corporate Bulletin Number 00-01-38-009B for more information. If leak dye has been added during a previous repair and has been in the vehicle for more than three years, it is recommended that additional dye be added. Finally, a leak check of the entire A/C system should be performed before the vehicle goes back on the road.
Courtesy of General Motors.

MACS Recommended Service Procedures

MACS Recommended Service Procedures © MACSW December 2005 1 of 23 Revision December 2005 MACS Recommended Service Procedures Initial Customer Contact It is important to obtain information from the customer identifying the problem and any previous servicing history prior to attempting repair of the system. • Use of the MACS “Air Conditioning & Heater Customer Questionnaire” will help identify the problem. • Identify service activity on MACS “A/C – Heating – Ventilation – Cooling System Checklist.” Identification of Type of Service Mobile A/C systems are an integral part of the total vehicle and operation of engine cooling fan(s) and the A/C compressor can be controlled by the vehicles’ computer systems resulting in a direct effect on system operation. Cooling Operation • Lack of cooling can be due to many reasons including: o Compressor operation o System Refrigerant Charge and Type ƒ Contaminated refrigerant ƒ Air in system ƒ Too much oil in system ƒ Sealant in system blocking/restricting controls/screens o System controls ƒ Including temperature door movement and proper position ƒ Defective/improperly operating (setting drift) thermostatic expansion valve ƒ Restricted or missing orifice tube ƒ Defective/improperly operating compressor clutch cycling switches ƒ Defective/improperly operating evaporator temperature sensors/thermistors or thermostatic switches ƒ Defective control valves (in variable displacement compressors) o Airflow circuits ƒ Clogged evaporator core fins (or condensate screen/filter) ƒ Plugged cabin air filter MACS Recommended Service Procedures © MACSW December 2005 2 of 23 Revision December 2005 o System mode door position o System fan motor, fan clutch and electrical controls o Condenser -- Insufficient airflow, restriction and/or capacity or improper substitute o Cooling System – Insufficient radiator performance or coolant condition and level o Material between radiator and condenser o Other cooling system malfunctions such as low coolant, a stuck closed or improperly functioning thermostat, lack of or improper electric cooling fan operation, defective mechanical fan clutch, defective or incorrect pressure cap, defective or improperly operating coolant control valve, etc. • Outside air ingestion • Internally blocked components (such as condensers, orifice tubes, etc.) • Replacement parts that do not meet or exceed the performance of OEM components Heating - Defrosting Operation The basic areas to check include: • Internally restricted heater core, flow restrictors or hoses • Coolant flow/coolant pump operation • System controls o Including temperature door movement and proper position o Operation of heater engine coolant flow valve, if installed and part of system o Pulse Width Modulated (PWM) temperature control operation of heater coolant valve and control circuit if installed and part of system • Airflow circuits o System mode door function and correct travel positions o System fan motor and electrical controls Visual Inspection Mechanical • Inspect compressor drive belt o Improper compressor operation due to: ƒ Excess wear – cracked – glazed MACS Recommended Service Procedures © MACSW December 2005 3 of 23 Revision December 2005 ƒ Incorrect tension – causing slippage o Compressor clutch ƒ Indication of overheating or slipping • Due to incorrect air gap • Oil coating • Poor electrical connection or low clutch voltage • Poor electrical ground connection, loose, corroded • Wrong or improper clutch Noise or Component Failure • Inspect for worn – damaged – broken o Engine mounts o Check compressor mounting bolts and brackets for proper torque and attachment o Engine torque struts o Improper refrigerant or heater hose routing and mounting o Improper charge, refrigerant, lubricant or amount o OEM bulletins o Aftermarket sealants Condenser • Operation of engine cooling fan(s) o Improper mounting (upside down), loose or missing hardware o Excessive fan motor current draw o Broken, cracked or missing fan blades o Malfunctioning dual function pressure switches (fan operation & compressor cut-out) o Missing orifice tube • Restricted airflow o Reduced airflow due to: ƒ Foreign material in fins (bugs, grass, etc.) • Between condenser and radiator ƒ Damaged condenser fins ƒ Missing or misplaced airflow seals ƒ Improper cooling fan(s) operation MACS Recommended Service Procedures © MACSW December 2005 4 of 23 Revision December 2005 System Airflow To assure that the system is delivering maximum airflow the following areas should be inspected for blockage. • Outside air operation o Check cowl and system air intake for restrictions ƒ System air inlet location for • Debris • Plugged cabin air filter • Recirculated air operation o System air inlet ƒ Debris • Plenum-Case/Duct Assembly o Plugged evaporator inlet filter o Deteriorated foam seals at ducting in plenum connections o Evaporator case condensate drain plugged ƒ (Can result in wet vehicle carpet) Confirm There Is Refrigerant In System System Has Pressure • Determine if the system has refrigerant pressure o To prevent damage to service equipment from possible refrigerant contamination, the system refrigerant should be checked with a refrigerant identifier and sealant detector. • HFC-134a pressure is approximately the same as the surrounding temperature. At an area temperature of 75 degrees F. the stabilized system pressure with A/C system off will be around 75 psig. o If the engine compartment is hot and system is off, pressure may be slightly higher. System Has No Pressure (15-0 PSI) (Note: If service port valve seals are damaged, they may not allow the valve cores to depress properly, possibly making it appear that the system does not contain pressure when it actually does.) MACS Recommended Service Procedures © MACSW December 2005 5 of 23 Revision December 2005 A visual inspection for evidence of system lubricant on the refrigerant system component(s) surfaces generally indicates potential refrigerant leak points. If the system is empty and does not have any refrigerant pressure, there are two approaches that can be used in an attempt to identify the leak point(s). Vacuum Method • Connect a vacuum pump to the system service ports and attempt to draw the system into a vacuum. If this is successful: o With vacuum pump off determine if the system will hold vacuum (at least 10 minutes) o Determine if there is a noise from an identifiable leak point. • Sometimes reducing the system into a vacuum can result in the leak point becoming sealed and the leak point not found. To determine if there is a system leak the pressure method should be used. Pressure Method To provide system refrigerant pressure for leak detection, only a partial system refrigerant charge is required. Generally an amount equal to 20% of the total system charge will result in a saturated system pressure reading. Once the system contains both liquid and vapor refrigerant the system pressure will not increase by adding more refrigerant. (See Figure 1) The refrigerant can be added without evacuating the system since upon its removal the recycling equipment will remove the air during the recycling process. Adding refrigerant to a system that did not have pressure will result in a slightly higher pressure as compared to pure refrigerant in the system. MACS Recommended Service Procedures © MACSW December 2005 6 of 23 Revision December 2005 Partial Refrigerant Charge 0 20 40 60 80 100 120 Refrigerant Service Fitting Pressure High/low side No Vacuum Prior Vacuum Pure Refrigerant Refrigerant & Air Saturated System Pressure with liquid/vapor at 85 degrees F. Figure 1 • With at least 50-psig system pressure perform the leak checking process. • If the refrigerant system is to be operated, install the full factory charge amount. Performance Testing Upon completion of the initial visual inspection and determination as to whether or not the system has pressure, it would be best at this time to conduct a system performance test. Running a performance test can offer an opportunity to see if the system will cool properly after repair(s) have been performed. It may also help eliminate possible future concerns and questions. If it has been determined that the system has a functioning or somewhat functioning compressor, a sufficient charge of refrigerant should be added to enable the compressor to operate to complete a performance test of the system. The performance test may also allow the technician to note if the compressor is functioning properly, if the compressor is noisy, if the expansion valve is functioning, if there is the expected temperature drop at the condenser, if there may be air blend door issues, or if the system may have any additional cooling issues. Having a sufficient MACS Recommended Service Procedures © MACSW December 2005 7 of 23 Revision December 2005 charge of refrigerant in the system will also ensure the system contains adequate internal pressure for use of an electronic leak detector. If fluorescent dye is to be used in a leak detection process, it may also be added at this time. System Refrigerant Leakage System refrigerant leaks can occur in many locations where they may be difficult to visually pinpoint. Visual inspection for evidence of system lubricant generally indicates potential refrigerant leak points. When a point is identified, use an SAE certified leak detector to verify the leak. Except for compressor shaft seals, surfaces that have evidence of lubricant generally indicate the presence of a refrigerant leak. In some cases, even though there may be a sign of lubricant leakage at a compressor shaft seal, the leak may be too small to result in a sufficient release of refrigerant which could be identified with a leak detector. The condenser, evaporator and rigid pipes/tubing, unless physically damaged, will not usually experience leakage. However, these components can be susceptible to corrosion, which could result in leakage. In general, operational leakage or mis-assembly of the following system components can result in system leak points. • Coupled flexible hose(s) o At hose and metal coupling connection o At quick connect points if moved • Compressor o Shaft seal o Porous casting/shell case seals o Pressure switches and/or o-rings o Pressure relief valve • System service ports due to: o Missing or lost service caps o Leaking/damaged core valves MACS Recommended Service Procedures © MACSW December 2005 8 of 23 Revision December 2005 • All refrigerant coupling points o O-Rings ƒ Cut/damaged ƒ Wrong size O-ring (diameter, thickness) ƒ Residual flush material, sealants, alternate refrigerants o Flat surface seals – gaskets ƒ Cut/damaged ƒ Incorrect torque of connections ƒ Residual flush material, sealants, alternate refrigerants Identification of System Refrigerant Leakage Identification of a small system refrigerant leak may require a combination of leak detection methods. If a system has at least 50-psig pressure, the system can be checked with an electronic leak detector. It should be noted that there is a major difference between the capabilities of electronic refrigerant leak detectors to find small leaks even though they are certified to the SAE standard. Increasing System Refrigerant Pressure for Leak Detection Elevating the temperature (warming) of all the A/C system components will help increase the system pressure for leak detection. (It is preferred to work on vehicles when the ambient temperature is above 70 degrees F.) Increase System Refrigerant Pressure Procedure (Using Engine Heat) • A/C System Controls o Turn compressor off so it will not operate. (Note: On some vehicles, particularly those equipped with Automatic Temperature Control systems, this may not be possible. It may be necessary to electrically disable the clutch by removing the clutch control relay, disconnecting the clutch field coil’s electrical connector, removing a fuse, etc. Also, some vehicles are equipped with clutchless compressors. Clutchless compressors operate any time the engine is running. If a vehicle is equipped with a clutchless compressor, refer to the vehicle manufacturer’s service information to see if a procedure exists to operate the engine without the compressor also operating.) MACS Recommended Service Procedures © MACSW December 2005 9 of 23 Revision December 2005 • Set panel system controls o Outside air (not max or recirculated) o High fan speed o Airflow from panel outlets o Temperature position max cold • Vehicle hood open to allow warm engine air to enter cowl inlet to A/C system • Operate engine idle condition o Neutral (park) with parking brake applied ƒ Depending on engine compartment temperature ƒ Run engine to warm up A/C system components for 15 minutes o After idling engine for 15 minutes (hot condition) o Shut engine and A/C fan off and start the leak detection process Other Leak Detection Methods Soap Bubbles Using soap bubbles to detect a leak will only identify a large leak. A leak rate producing 1 bubble per second results in a loss of over 50 ounces per year. Since most mobile systems contain only one half of that amount, they will lose cooling capability within days. As noted in figure 2 the typical R134a single evaporator system charge is 25.6 ounces. The information found in figure 2 compares the detection rate of an SAE leak detector of 0.5 ounces per year with water and soap bubble detection methods of 45 to 55 ounces per year. The use of soap bubbles may help in verifying the location of large leaks in tight and hard to access places or near multiple refrigerant connections. Unless the system has a large refrigerant leak, using soap bubbles for leak detection is an ineffective method when servicing mobile A/C systems. MACS Recommended Service Procedures © MACSW December 2005 10 of 23 Revision December 2005 Refrigerant Leak Detection Capability 0 10 20 30 40 50 60 WATER BUBBLE SOAP BUBBLE J1627 SAE SPEC. Refrigerant Loss Ounces/year Identifiable Leak Rate 1 bubble per second SAE Identifiable Leak Rate 0.5 ounce [14g] per year Average Single Evap. System Charge 2000 - 2004 MY 25.6 Ounces Figure 2 Using Nitrogen Using nitrogen for leak checking is a questionable method due to a lack of nitrogen detection equipment and nitrogen’s high pressure. For example, if an evaporator core is subjected to over 300 PSI, it may burst. As the components age, they may fail at pressure less than 300 PSI. Nitrogen and soap bubbles have been used in the commercial refrigerant industry on large systems that are prone to high leakage rates. Using nitrogen and soap bubbles for locating small leaks in mobile A/C systems is of questionable value. Using Other Refrigerants The use of R22 or other chemicals having higher pressure can result in system damage. Use of R22 for leak checking can result in chemical damage to the system over time (especially to seals). The R22 cannot be completely removed from the system after leak checking. MACS Recommended Service Procedures © MACSW December 2005 11 of 23 Revision December 2005 The R22 remaining in the system’s lubricant may over time chemically damage hose and seal material resulting in a potential later system failure. Using R22 is never recommended for use for leak checking. Check system and/or component manufacturers' policy on using other refrigerants. Using Trace Dye When trace dye is installed in the system it requires that the lubricant carry it to the leak point. This may not be an immediate action and may require hours of system operation, depending upon the system’s use, before the dye will be visible when using a test lamp. Dye installed in the system may not be visible depending upon its original expected lifetime and its visibility can be reduced after being exposed to air (point of leak) and may not be identifiable the next season. If too much dye is added to the system, it can affect compressor durability by changing the lubricating ability of the system’s oil and restricting oil flow through the refrigerant system. Using Vacuum Decay Using a vacuum decay method will only confirm you have a leak. Unless very large, it does not give the location. You may also have a leak in your measuring equipment. In addition, using a vacuum decay method may not find some leaks, because when the system is under vacuum the leak point (o-ring – seal – hose) may seal and leak only when under pressure. Electronic Detector Component Leak Checking • Leak test with the engine off o Do not contaminate the detector probe tip with dirt, grease or expose it to a direct stream of refrigerant. o If component being checked is dirty, wipe it off with a clean shop towel or blow off with dry shop air. ƒ Do not use cleaners or solvents. • Detectors may react to their chemical composition. ƒ Leak test the entire refrigerant system, testing all lines, fittings and components. • If a leak is found, continue to test the remainder of the system for potential additional system leaks. ƒ Move the probe around the location, at a rate no more than 25 to 50 mm/second (1 to 2 in/second), MACS Recommended Service Procedures © MACSW December 2005 12 of 23 Revision December 2005 ƒ Hold the sensing probe no more than 5 mm (1/4 in) from the surface completely around the area being checked. • Moving the sensing probe slowly and as close as possible to the component improves the chance of finding a leak. ƒ Confirm the leak by blowing shop air into the area of the suspected leak to disperse any refrigerant that may not be due to the suspected leak. • Repeat if necessary. • Blowing out the area with shop air often helps locate the exact position of large leaks. • Leak testing of evaporator core o Run the air conditioning blower on high speed for 15 seconds minimum. ƒ Turn blower off, wait 5 minutes for the refrigerant to accumulate in the case. • Insert the leak detector probe into the o Blower resistor block opening or o Evaporator case drain hole if there is no condensation, or o Since refrigerant is heaver than air, locate the lowest point in the duct system. Do not rely on an indication of a leak with the probe located in panel outlet. o Into the closest opening in the heating/ventilation/air conditioning case to the evaporator. ƒ If the detector alarms, an evaporator leak has apparently been found. ƒ (Note: On R12 systems there will be a covering of oil and dirt on the evaporator. On R134a systems there may not be since the lubricant is water soluble. Therefore check condensate drain for dye products.) Leak Detectors Meeting SAE J1627 Depending upon the technology used for a leak detector, false triggering may occur from foam seals and adhesives used around the evaporator. Some detectors meeting J1627 are calibrated to detect only R12 and R134a refrigerants, thus eliminating the possibility of false leak identification. MACS Recommended Service Procedures © MACSW December 2005 13 of 23 Revision December 2005 System Lubricant Charge There is no effective way in the field to determine the amount of lubricant that is in a system. Systems with too much oil can result in reduced cooling capacity. Excessive lubricant results in the internal coating of the evaporator or condenser resulting in less heat transfer. Only the A/C system and component manufacturer’s recommended lubricant type, viscosity and amount should be used to provide the maximum cooling performance and compressor durability. To establish the correct amount of lubricant in a system, each component must be drained or liquid flushed (using approved chemicals and procedures) and the manufacturer's recommended lubricant amount for the specific system be added. System Refrigerant Charge The system pressure cannot be used to determine the amount of refrigerant in a system. To assure that the system is operating properly, the refrigerant should be recovered from the system and the correct amount installed with properly calibrated charge equipment. “Top Off” service procedures will result in improper refrigerant charge amounts and is not considered professional servicing. Establishing System Refrigerant Charge Amount Mobile A/C systems are operated over a great variation of system loads, from low loads to hot weather soak and cooldown conditions. To assure that a continuous source of liquid refrigerant is supplied to the expansion device, the vehicle manufacturer establishes the charge amount for high load conditions. When the system refrigerant charge amount is determined, several factors are included in the selection of the charge value to ensure system performance. These factors include small losses from servicing procedures and lubricant circulation in the system. Mobile A/C system refrigerant charging should not be attempted by using high and low side pressure readings. Using high and low side pressure readings are commonplace for charging commercial systems, since they generally operate under constant load conditions. Unlike commercial A/C systems, on any given day, a mobile A/C system could be required to operate from hot vehicle soak and cooldown to reduced stabilized MACS Recommended Service Procedures © MACSW December 2005 14 of 23 Revision December 2005 highway cooling demand conditions. Under all these conditions, an adequate amount of liquid refrigerant must be available to provide maximum system cooling performance. TXV System A typical expansion valve system can be found in figure 3. The TXV can either be a separate in-line device or a block valve located near the evaporator. Figure 3 The charge curve identified in figure 4 shows the variation in system pressure under high load conditions for a production system. The factory system charge was established at 28 ounces. For this condition the system pressure change between 22 to 28 ounces of refrigerant in the system was 5-psig on the high side and 4-psig on the low side. Depending upon the temperature in the service bay and the load on the A/C system, it is impossible to duplicate charging conditions that rely upon pressure reading for every type of mobile A/C system serviced. Using the pressure values identified on the left side of the flat portion charge curve, charging to 295-psig high side and 22-psig low side could be in the range of 22 ounces. With only a slight system refrigerant loss the system would have reduced cooling performance and the potential for inadequate system lubricant circulation. Charging to MACS Recommended Service Procedures © MACSW December 2005 15 of 23 Revision December 2005 the right side of the charge in the 30 to 32 ounce range could result in the system being shut off on a hot day in city traffic. Since the capacity of the receiver-drier limits the amount of excess refrigerant that can be added to the system, systems that incorporate the integral receiver-drier/condenser design have less internal refrigerant storage capability as compared to a separate RD system. The correct factory refrigerant charge is required to avoid overcharging the system. System Charge Curve 108F Ambient 40 MPH 78 65 61 61 60 60 58 57 16 20 22 24 26 28 30 32 225 260 295 295 295 300 310 345 0 50 100 150 200 250 300 350 16 20 22 24 26 28 30 32 Ounces R134a Outlet Temperature Suction Pressure Head Pressure System Charge 28 Ounces Head Pressure PSIG Suction Pressure PSIG Panel Outlet Temperature Degrees Figure 4 Refrigerant Overcharge Symptoms A typical system overcharge problem may not be evident on a cool morning or in the service bay during low heat load conditions. Excess refrigerant will result in increased high side system pressure, when the system is operated during high heat load conditions. The excessive pressure will cause the high side pressure switch to shut off the compressor when conditions such as idle and stop and go driving are encountered. Although an electric or mechanically engine driven fan should be operating during low speed operation, the amount of airflow may not be enough to handle the heat load. Considering that most passenger cars and light trucks have electric engine cooling fan(s), during idle conditions, the effect of wind can influence airflow through the condenser. Side or tail wind during city traffic and idle conditions can result in loss of A/C system cooling due to the pressure discharge (PD) switch shutting off the MACS Recommended Service Procedures © MACSW December 2005 16 of 23 Revision December 2005 compressor. At road speeds, increased airflow over the condenser allows the compressor to re-engage, but may still result in higher discharge pressures, causing warmer outlet air temperatures. Orifice Tube System A typical orifice tube system can be found in figure 5. Figure 5 The charge curve in figure 6 is for an orifice tube system having a factory refrigerant charge of 26 ounces. As compared to the TXV system, the high side curve is more gradual as additional refrigerant is added. This is due to the refrigerant being stored in the accumulator on the low side of the system. MACS Recommended Service Procedures © MACSW December 2005 17 of 23 Revision December 2005 Figure 6 With professional service equipment, less time will be consumed installing the correct system refrigerant charge, ensuring the proper operation of the A/C system as compared to charging by questionable gauge pressure readings. Not being able to identify how much refrigerant is in the system results in the potential for improper system operation. Systems that are overcharged become an environmental concern due to the potential release of the excess refrigerant. Systems not having the correct refrigerant charge may result in many unseen problems. Low refrigerant charge can result in: Poor system performance; evaporator core refrigerant distribution problems can result in temperature spread across panel outlets and localized core icing (freeze up), reducing system airflow. Reduced cooling performance will occur due to a lack of solid flow of liquid refrigerant (partial vapor) being supplied to the evaporator under high loads. Since lubricant circulation in the system relies upon a proper system refrigerant charge, inadequate refrigerant and lubricant will result in increased compressor operating MACS Recommended Service Procedures © MACSW December 2005 18 of 23 Revision December 2005 temperature and potential compressor failure. In addition, the excess temperature can result in damage to the lubricant, flexible hoses and seals. Not all lubrications are compatible with a mobile A/C system. There are some lubricants which will not be transported in sufficient quantities to service the compressor. The information found in figure 7 compares a reduced system refrigerant charge’s effect on the compressor discharge temperature. This is something that is not identifiable by just looking at the system operating pressures. The production charge for this system is 26 ounces. By reducing the charge by 6 ounces (to 20 ounces) the high side pressure was reduced by 21 psig (from 239 to 218) and the low side pressure was 6 psig lower (from 38 to 32). Panel outlet temperature is four degrees cooler with the 6 ounce reduced charge (58 vs. 62). Unfortunately, when charging the system by using the pressure and panel outlet temperature, a reduced system charge could occur. The undetectable temperature problem is the compressor outlet temperature, which increased from 150 F to 182 F for the reduced 6-ounce charge, and with a reduced charge of 8 ounces was 204 degrees F. Figure 7 MACS Recommended Service Procedures © MACSW December 2005 19 of 23 Revision December 2005 Compressor Failure Should a system experience an internal compressor failure, it may not be possible to completely clean the system of the debris from the failure. Since heat exchangers (evaporator/condenser) have very small multiple internal passages and internal baffles, flushing may not clean all passes returning the heat exchanger to its expected level of performance. Replacement of an orifice tube or replacing the expansion valve must be done to assure maximum performance. Replacement of the accumulator or receiver dryer is necessary when an internal compressor failure has occurred. Flushing of flexible hoses and refrigerant lines is may be required as well as the installation of auxiliary filters or compressor screens. Hose assemblies having inline mufflers should be replaced, since flushing may not remove all the debris from the failure. Liquid lines that contain permanent orifice tubes must be replaced. Installation of non-restrictive inline filters minimizes the chances of the re-circulation of any foreign material remaining in the system. Movement of debris can reverse flow from the system high side to low side when the system is shut off and equalizes, resulting in the contamination of low side components (the accumulator and evaporator). Refrigerant Removal It is extremely difficult to completely remove all refrigerant from the system. When the system is being evacuated, the refrigerant boiling (changing from liquid to vapor state) results in cooling of the system components. The lubricant also adsorbs the refrigerant and the evacuation process is slow in removing the refrigerant from the lubricant. Raising the temperature (warming) of all the A/C system components and reducing the system to at least 20 inches of vacuum, will help recover the maximum amount of the refrigerant in the shortest period of time. Removal Procedure o Turn off the compressor so it will not operate. (Note: On some vehicles, particularly those equipped with Automatic Temperature Control systems, this may not be possible. It may be necessary to electrically disable the clutch by removing the clutch control relay, disconnecting the clutch field coil’s electrical connector, removing a fuse, etc. Also, some vehicles are equipped with clutchless compressors. Clutchless compressors operate any time the engine is running. If a vehicle is equipped with a clutchless MACS Recommended Service Procedures © MACSW December 2005 20 of 23 Revision December 2005 compressor, refer to the vehicle manufacturer’s service information to see if a procedure exists to operate the engine without the compressor also operating.) • Set panel system controls o Outside air (not max or recirculated) o High fan speed o Airflow from panel outlets • Vehicle hood open to allow warm engine air to enter cowl inlet to A/C system • Operate engine idle condition o Neutral (park) with parking brake applied ƒ Depending on engine compartment temperature • Run engine to warm up A/C system components for 15 minutes • After idling engine for 15 minutes (hot condition) • With engine idling and A/C fan high, system on outside air, start refrigerant recovery process • When refrigerant recovery is completed, including the required 5 minute recheck for system pressure (system refrigerant out gassing), shut vehicle and equipment off. Desiccant Replacement The purpose of desiccant in a mobile air conditioning system is to absorb and hold moisture. Moisture in a system (above an acceptable level) can lead to corrosion and degradation of the lubricant. The general industry recommended desiccant replacement service guidelines are found in table1. Desiccant material is located in the refrigerant circuit. Servicing of the desiccant will depend upon its location. The location may not allow the replacement of only the desiccant material, resulting in the replacement of an accumulator, or a receiver drier assembly. Systems having an integral receiver drier condenser assembly may have the service feature that allows replacement of the desiccant pack. MACS Recommended Service Procedures © MACSW December 2005 21 of 23 Revision December 2005 Table 1 Recommended Guidelines for Replacement of Desiccant Service Operation Replace RD/Accl or Desiccant Pack Yes w/Replace Compressor (Ref System contains foreign material) X w/Replace Evaporator (Ref System contains foreign material) X w/Replace Condenser (Ref System contains foreign material) X w/Replace refrigerant line or hose (Ref System contains foreign material) X w/Replace Refrigerant Control OT/TXV (Ref System contains foreign material) X w/System has open line(s) more that 24 hours X w/System has operated over 5 years without desiccant replacement in high humidity area X w/System has operated over 10 years without desiccant replacement X Desiccant Replacement Guidelines Desiccant replacement guidelines vary among vehicle manufacturers and system, component and parts suppliers. To maintain the warranty on purchased parts, desiccant must be replaced as specified by the particular supplier whose parts are being installed. Flushing Systems Flushing of the mobile A/C system may not completely remove all potential foreign material from the system. Proper use of flushing solvents is important to accomplish the desired results. It is necessary to purge all residual flush material from the system when servicing. Any residual flush left behind will contaminate and dilute the A/C system oil charge. SAE standard J2670 provides testing and acceptance criteria for stability and compatibility of chemicals, including flushing materials and additives intended for use in R134a vehicle air conditioning systems. Use of non-compatible chemicals may result in future (extended time) failure of A/C system materials. MACS Recommended Service Procedures © MACSW December 2005 22 of 23 Revision December 2005 Flushing Material R134a is commonly used as a flushing solvent in conjunction with equipment capable of handling the refrigerant in such a manner. Because R134a can act as both the refrigerant and a flushing solvent, R134a is deemed to meet all the requirements set forth in the J2670 specification. Keep ion mind that R134a should only be used to flush lubricant and loose debris from an A/C system. R134a will not remove any particulate matter that has attached itself to the inner tube walls. Some A/C system and component manufacturers have developed flushing solvents and equipment for removal of foreign material from the system. In general, flushing provides a method of removing: -- Lubricant -- Residual materials found in the system -- Foreign material Removal of some foreign debris may not be achievable in heat exchangers due to the multipath circuits and the potential for the flushing procedure to bypass the plugged refrigerant flow path. To achieve the original level of performance, replacement of the heat exchanger may be required. In flushing a contaminated system, follow the procedures provided by the system or component manufacturer and by using the recommend flushing material and equipment. Evaporator Freeze Protection Loss of system cooling performance can occur if the system has an incorrect evaporator freeze protection setting. This condition can occur when the system has been operated for an extended period of time. When the evaporator fin surface is operated below 32 degrees F, the collected condensate water will turn to ice. This will then result in loss of system airflow as the frozen water blocks the air passages and the icing condition continues to spread over the core area. With an incorrect control setting, this loss of cooling can occur on systems that use a fixed displacement or variable displacement compressor. There are many options on how evaporator freeze protection is achieved. Some of the control methods include pressure control devices in the compressor body or attached to other refrigerant system MACS Recommended Service Procedures © MACSW December 2005 23 of 23 Revision December 2005 components. Other options include electronic sensors or thermal switches controlling compressor operation by sensing refrigerant component surface or outlet air temperature. It is important to identify how the system manufacturer controls evaporator freeze protection and that the correct pressure or temperature settings are used when servicing the system. AIR CONDITIONING & HEATING CUSTOMER QUESTIONNAIRE _______________________________________________________ CUSTOMER Name__________________________ Phone__________________ Date__________ Address________________________ City______________ State_____ Zip_______ _______________________________________________________ VEHICLE Year____________ Make____________ Model____________ Color____________ A/C System Type – ❒ Manual ❒ Auto. Temp. Control ❒ Dual / Rear Auxiliary Unit _______________________________________________________ PROBLEM / SYMPTOM ‰ No A/C ‰ No Heat ‰ No Defrost ‰ Poor Cooling ‰ Poor Heating ‰ Improper Fan/Blower Operation ‰ Air From Wrong Outlet(s) ‰ No Temperature Control ‰ Noise Inside Car ‰ Noise Under Hood ‰ Interior Water Leak ‰ Engine Coolant Leak ‰ Warning Light(s) On ‰ Odor ‰ Other* (See Below) WHEN DOES THE PROBLEM OCCUR? ‰ Always ‰ Intermittent ‰ When Hot ‰ When Cold ‰ At Start Up ‰ During Warm Up ‰ At Idle ‰ High Engine Speeds ‰ Driving Away From Stop ‰ At Road Speeds Have there been any previous attempts to repair this problem? ❒ No ❒ Yes If there were previous repair attempts, what was done? (What parts were installed, etc.) _____________________________________________________________________________ _____________________________________________________________________________ Did previous repairs help the problem? ❒ No ❒ Some ❒ A lot ❒ At first, but not now. Have repairs or service of any kind been recently performed to the vehicle? ❒ No ❒ Yes If so, exactly what was done? ______________________________________________________________________ ______________________________________________________________________ *FURTHER DESCRIPTION OF THE PROBLEM ______________________________________________________________________ ______________________________________________________________________

Air Conditioning Best Service Practices

Air Conditioning Best Service Practices Tried & Tested

When your car or truck has an air conditioning problem and needs service, what should you do? If your A/C system only needs some refrigerant, you can probably recharge the a/c system yourself. But if you are having cooling problems, leaks or electronic control problems, you should probably seek out a repair facility that specializes in air conditioning service work.

Our advice is to seek out a repair facility that is a member of MACS, the Mobile Air Conditioning Society. MACS is a non-profit trade association for repair shops that do air conditioning service work. MACS promotes training, education, professionalism, and most importantly "Best Practices" for servicing and repairing your vehicle's air conditioning system.

Since 1991, MACS has assisted more than one million technicians to comply with 1990 Clean Air Act requirements for certification in refrigerant recovery and recycling to protect the environment.

Recently, the Climate Protection Partnership division of the U.S. EPA teamed up with MACS to publish and promote six mobile air conditioning best service practices checklists. These checklists are written for professional technicians to help them environmentally safe and technically proper air conditioning service and repairs. The purpose of the checklists is make sure your vehicle is serviced correctly when you take it in for air conditioning service work.

If your shop is NOT following these practices, you should bring it to their attention - or take your vehicle to another shop who does follow the Best Practices recommendations.

Note: The Best Practices guidelines are voluntary recommendations, and are not required by law. Even so, they do reflect current thinking on the best ways to properly service and repair automotive mobile A/C systems. The input for these checklists was provided by highly experienced A/C technicians who are familiar with the right ways and wrong ways of servicing service A/C systems.

The A/C Best Service Practices Guidelines for A/C service include:

A/C Service (general)
Leak Detection
Refrigerant Recovery
System Charging
Field Repair and Assembly of A/C Hoses
A/C Equipment Maintenance.

Click Here for MACS Air Conditioning Best Practices Guidelines

R-1234yf Refrigerant

R-1234yf Refrigerant For Your Car

Auto makers are slowly moving toward a new refrigerant for automotive air conditioning systems. The new refrigerant is R-1234yf (HFO-1234yf), and it will be phased in slowly over time starting with some 2014 model year vehicles.

R-1234yf has cooling properties that are similar to R-134a, which has been used as an automotive refrigerant since it was introduced back in 1994 to 1995 to replace R-12. R-134a contains no CFCs, which are harmful to the Earth’s protective ozone layer, but it does retain heat well and has a relatively high Global Warming Potential (GWP) rating of 1410.

IMPACT ON GLOBAL WARMING

Automotive refrigerants that leak out of A/C systems contribute very little to the overall global warming problem, only about 0.14% according to scientific estimates. Even so, when you multiply the millions of vehicles that are AC-equipped times even a small amount of refrigerant leakage over time, the numbers can add up. Some would argue that switching to a new refrigerant is unnecessary and will hardly make a dent in climate change. Others argue that it is all a conspiracy by DuPont and Honeywell to monopolize the world automotive refrigerant market by getting regulators to require a new low global warming potential refrigerant. R-1234yf has a GWP rating of 4, which is over 350X less than R-134a!

Politics and conspiracy theories aside, regulations have already been passed in Europe that will require some type of new refrigerant. The Europeans were considering CO2 (R-744) because it has the lowest GWP rating of all: One! But A/C systems that operate using CO2 require extremely high pressures (1,800 to 2,200 PSI versus 300 to 400 PSI for R-134a and R-1234yf) and are much more expensive to manufacture.

The auto makers had agreed on moving ahead with R-1234yf until Daimler (Mercedes-Benz) ran some tests that revealed R-1234yf could ignite under certain special conditions. Based on the test findings, Mercedes and Volkswagen said no to the new refrigerant. R-1234yf is slightly flammable, but according to the Society of Automotive Engineers (SAE), the new refrigerant is safe for automotive passenger car use. The risk of fire is extremely remote in case of an accident or refrigerant leak into the passenger compartment.

To read the official SAE press release, Click Here.

hfo-1234yf refrigerant cooling performance chart

HOW DOES R-1234YF COMPARE TO R-134A?

R-1234yf has cooling performance that is similar to R-134a but not quite as good. It is about 5 percent less efficient than R-134a. It is not a simple drop-in substitute for R-134a because it requires a slightly larger or more efficient condenser and a more robust leak-resistant evaporator (for safety). R-1234yf also requires a new type of compressor PAG oil, as well as new J2843 certified recovery and recycling equipment designed especially for the new refrigerant. And here’s the punch line: R-1234yf is significantly more expensive than R-134a ($120 per pound versus about $10 per pound).

For more information, see HFO-1234yf Technical Information - Honeywell

Other hydrocarbon and hydrocarbon-blend refrigerants (such as propane, butane and others) have also been considered, but would require some type of secondary loop cooling configuration and special safety features to keep the potentially explosive vapors away from the passenger compartment. Many states ban the use of flammable refrigerants in motor vehicles (except for use in refrigerated truck trailer cooling units).

R-134A WILL CONTINUE FOR CURRENT VEHICLES AND OLDER VEHICLES

As of this writing, there are no plans to eliminate R-134a as happened to R-12, or to require retrofitting older vehicles or current vehicles that have R-134a A/C systems to the new HFO-1234yf refrigerant. R-134a will remain in production to service existing A/C systems.

R-134a should only be used in R-134a systems, and should NOT be used to top off a R-1234yf system. Likewise, R-1234yf should NOT be used in an older R-134a or R-12 A/C system due to material compatibility and lubrication issues.

R-1234yf A/C systems will have their own unique service fittings (which are different from R-12 and R-134 fittings) to discourage accidental cross-contamination.

R-1234YF SERVICE PRECAUTIONS

Because R-1234yf is slightly flammable, an evaporator that is leaking MUST be replaced with a new unit. The installation of a used evaporator from a salvage vehicle is NOT allowed because there is a chance it might also leak, exposing the vehicle's occupants to potentially flammable vapor mixture.

Professional service equipment for R-1234yf includes a leak check feature built into the recovery and recharging machine. The equipment also includes a refrigerant identifier to make sure the vehicle's A/C system contains R-1234yf and not some other refrigerant.

If your a/C system is leaking, the leak MUST be fixed before the shop will recharge your A/C system with refrigerant.

R-1234yf NEW CAR APPLICATIONS

The first U.S. vehicle to use R-1234yf refrigerant was the 2013 Cadillac XTS. Cadillac also tried R-1234yf in the Cadillac ATS, but stopped only one month into production because of A/C compressor noise and vibration issues. Early production ATS models were recalled and retrofitted back to R-134a (which apparently works fine in an A/C system designed for R-1234yf).

For model year 2014, R-1234yf is used in the Jeep Cherokee, Chrysler 300, Dodge Ram 1500, and Dodge Charger, Challenger and Dart. It will also be used in the 2015 Chrysler 200.

Most auto makers are expected to have numerous R-1234yf applications by model year 2017 and beyond. Auto makers receive fuel economy credits for vehicles that are converted to R-1234yf, which helps them achieve the new higher Corporate Average Fuel Economy (CAFE) requirements.

Update February 2015

R-1234yf Vehicle Applications:

Here is a list of late model vehicles sold in North America that are using R-1234yf refrigerant in their air conditioning systems:

BMW i3 Electric
Cadillac XTS (2013 and 2014)
Chevrolet Malibu
Chevrolet Spark EV (2014)
Chevrolet Trax
Chrysler 300 (2014)
Dodge Challenger (2014)
, Honda Fit EV (2013 and 2014)
Hyundai Santa Fe & i30
Ford Transit
Infinity Q50
Jeep Cherokee (2014)
Kia Sorento, Optima & Cadenza
Mazda CX-5
Mitsubishi Mirage
Range Rover and Range Rover Sport (2014)
Subaru BRZ, Forrester & Impreza

Refrigerant Resources:

HFO-1234yf Technical Information - Honeywell

Alliance for Responsible Atmospheric Policy (ARAP)

DuPont Refrigerants

EPA FAQs on Alternative Refrigerants

Alternative Refrigerants

Alternative Refrigerants For Your Vehicle

As R-12 continues to disappear, the price of R-12 refrigerant continues to rise. So what do you recharge an older air conditioning system with if R-12 is unavailable?

DROP-IN ALTERNATIVES FOR R-12 REFRIGERANT?

Though a number of alternative refrigerants are marketed as "drop-in" replacements for R-12, there is really no such thing as a true drop-in replacement. The reason why is because Federal law prohibits the topping off A/C systems with ANY refrigerant that is chemically different from what is already in the system, unless all of the old refrigerant is first removed so the system can be converted to the alternative refrigerant.

There are, however, a number of alternative refrigerants that can be used in older vehicles with R-12 A/C systems, and most have been reviewed and approved by the EPA for retrofitting older R-12 A/C systems. Approved refrigerants must meet the EPA's SNAP (Significant New Alternatives Policy) criteria for environmental acceptability and usage.

NOTE: The SNAP rules prohibit the use of flammable refrigerants (propane, butane and similar hydrocarbons) in mobile A/C systems because of their hazardous nature, and the SNAP rules prohibit the use of any other refrigerants that contain ozone-damaging CFCs. for more information about flammable refrigerants, Click Here.

APPROVED ALTERNATIVE REFRIGERANTS

There are number of alternative refrigerants from which to choose. One is R-134a, which is the ONLY alternative refrigerant currently approved by all vehicle manufacturers for retrofitting older R-12 A/C systems. The vehicle manufacturers say R-134a will cool reasonably well in most R-12 A/C systems provided the proper retrofit procedures are followed. They also recommend R-134a because it is a single component refrigerant, unlike most of the alternatives which are actually BLENDS of two to more ingredients.

The vehicle manufacturers do not like blends because blends can undergo "fractionation." This is when the individual ingredients in a blend separate for various reasons. Fractionation can be caused by chemical differences between the refrigerants (lighter and heavier elements do not want to stay mixed), different rates of leakage through seals and hoses (smaller molecules leak at a higher rate than larger ones), and different rates of absorption by the compressor oil and desiccant. Fractionation is a concern because it can change the overall composition of the blend once it is in use, which can affect the performance characteristics of the refrigerant. Fractionation also makes it difficult to recycle a blended refrigerant because what comes out of the system may not be the same mix that went into the system.

If you would like to read a variety of different views on the subject of alternative refrigerants and retrofits, Click here.

The vehicle manufacturers also say limiting the alternatives to one choice (R-134a) simplifies things, reduces the risk of cross-contamination and eliminates the need for multiple recovery machines. EPA rules require a separate dedicated recovery only or recovery/recycling machine for each type of refrigerant serviced.

ALTERNATIVE REFRIGERANT BLENDS

Alternative refrigerants that have been found acceptable for automotive applications or are currently being reviewed by the EPA include the following blends:

Free Zone (RB-276). Supplied by Refrigerant Gases, this blend contains 79% R-134a, 19% HCFC-142b and 2% lubricant.

Freeze 12. Supplied by Technical Chemical, this blend contains 80% R-134a and 20% HCFC-142b.

FRIGC (FR-12). Made by Intermagnetics General and marketed by Pennzoil, this blend contains 59% R-134a, 39% HCFC-124 and 2% butane.

GHG-X4 (Autofrost & McCool Chill-It). This blend is supplied by Peoples Welding Supply and contains 51% R-22, 28.5% HCFC-124, 16.5% HCFC-142b and 4% isobutane (R-600a).

GHG-HP. Also supplied by Peoples Welding Supply, this blend contains 65% R-22, 31% HCFC-142b and 4% isobutane (R-600a).

Hot Shot\Kar Kool. Supplied by ICOR, this blend contains 50% R-22, 39% HCFC-124, 9.5% HCFC-142b and 1.5% isobutane (R-600a).

The suppliers of the alternative blends say their products typically cool better than straight R-134a in systems designed for R-12, and do not require changing the compressor oil or desiccant in some cases. Changing the desiccant to XH-7 is usually recommended if an R-12 system is converted to R-134a. The desiccant should also be replaced if a blend contains R-22 because R-22 is not compatible with XH-5 or XH-7 desiccant. The recommended desiccant in this case would be XH-9.

The suppliers of the alternative blends also insist the fractionation problem is exaggerated and do not foresee any major problems with recovering and recycling their products (recycling blends is currently illegal, but the EPA is reviewing its feasibility).

One supplier of these products say they sold several million pounds of their alternative refrigerant, so the public is accepting it.

MACS ALTERNATIVE REFRIGERANT FIELD STUDY

A field study of various refrigerants conducted by the Mobile Air Conditioning Society (MACS) in 2003 compared the cooling performance of R-12, R-134a and three blended refrigerants (Freeze 12, FRIGC and McCool Chill-It). The study found that all the alternative refrigerants (including R-134a) did not cool as well as R-12 in the vehicles tested (a 1990 Pontiac Grand Am and a 1987 Honda Accord). But the study did find that the blends outperformed R-134a in the Honda (but not the Pontiac). The increase in A/C outlet temperature with the different refrigerants ranged from less than a degree to almost 11 degrees.

ILLEGAL REFRIGERANTS

Another class of alternative refrigerants has also appeared on the scene: illegal refrigerants. Some products that have been introduced (OZ-12, HC-12a, R-176 and R-405a) do not meet the EPA criteria for environmental acceptability or safety. Flammable refrigerants such as OZ-12 and HC-12a that contain large quantities of hydrocarbons (propane, butane, isobutane, etc.) have been declared illegal for use in mobile A/C applications, but are still turning up in vehicle systems anyway because of their cheap price.

WARNING: Flammable refrigerants pose a significant danger to the occupants inside a vehicle should a leak occur. A spark from a cigarette or a switch can ignite the leaking refrigerant causing an explosion and turning the car into a bomb. It only takes about four ounces of a flammable hydrocarbon refrigerant such as propane or butane to create an explosive mixture inside a typical automobile passenger compartment.

Frontal collisions can also release the refrigerant if the condenser is damaged, which could result in a severe underhood fire causing extensive damage to the vehicle.

There is also a risk to service technicians and do-it-yourselfers who might encounter leaks while servicing a vehicle or operating recovery/recycling equipment.

Merely topping off an A/C system with a flammable hydrocarbon can make the entire charge of refrigerant flammable if the amount added exceeds a certain percentage: 10% in the case of an R-12 system and only 5% with R-134a! That is only three or four ounces of hydrocarbon depending on the overall capacity of the system.

Flammable refrigerants are used in some stationary applications as well as truck trailer refrigeration units because there is less risk of leakage or fire. Also, the amount of refrigerant is typically much less, only five or six ounces total instead of several pounds.

BOOTLEG REFRIGERANTS

Less dangerous but equally illegal is bootleg R-12 that is being smuggled into the U.S. from offshore. Though most of the industrialized nations have stopped manufacturing R-12 (production ended in the U.S. December 31, 1995), R-12 is still being made in some Third World countries including Mexico. Some of this product is finding its way past customs in mislabeled containers or concealed in various ways. The EPA warns that much of the refrigerant it has confiscated thus far is of poor quality, contaminated by air, moisture, R-22 and other substances. The EPA has worked with customs authorities and the FBI to make a number of arrests. Fines for violating the clean air rules can run up to $25,000 per instance.

Counterfeiting branded product is another scam that is being perpetrated to turn a fast buck in today's market. Cylinders of counterfeit Allied Signal Genetron R-12 have reportedly been turning up in various parts of the country. The cylinders do not contain R-12 but some "unknown" refrigerant. Allied Signal says the counterfeit boxes do not have cut-outs where lot numbers strapped on cylinders would appear and there are no bar codes or white painted stripes on the sides. The number "Q 1167" may also appear on the bottom of the packaging. The cylinders themselves may be marked with a pressure-sensitive decal whereas the genuine product has markings printed on the cylinder itself.

CONTAMINATED REFRIGERANT

The high price of R-12 has also lead to an increase in incidences of virgin R-12 being adulterated with other less expensive refrigerants. Most technicians assume a tank of virgin refrigerant is pure, but some are finding that is not the case. Some suppliers say they now test every single tank of refrigerant to make sure it contains the proper refrigerant and that the quality of the refrigerant meets specifications.

The primary threat of contamination, though, is that of accidentally cross-contaminating refrigerants when vehicles are professionally serviced. Because the law requires all refrigerants to be recovered, there is a potential risk of contaminating when recovery and recycling equipment is connected to a vehicle. The problem is compounded, many say, by the proliferation of alternative and illegal refrigerants.

The dangers of cross-contamination are the effects it can have on cooling performance and component reliability. R-12 and R-134a are not compatible refrigerants because R-134a will not mix with and circulate mineral-based compressor oil (which may lead to compressor failure). Nor is R-134a compatible with the moisture-absorbing desiccant XH-5, which is used in many R-12 systems.

Intermixing refrigerants can also raise compressor head pressures dangerously. Adding R-22 (which is used in many stationary A/C systems but is not designed for use in mobile A/C applications) to an R-12 or R-134a system may raise head pressures to the point where it causes the compressor to fail. Straight R-22 can cause extremely high discharge pressure readings (up to 400 or 500 psi!) when underhood temperatures are high. R-22 is also not compatible with XH-5 and XH-7 desiccants used in most mobile A/C systems.

R-134a also requires its own special type of oil: either a polyakylene (PAG) oil or a polyol ester (POE) oil. The OEMS mostly specify a variety of different PAG oils because some compressors require a heavier or lighter viscosity oil for proper lubrication (though General Motors does specify only a single grade of PAG oil for most service applications). The aftermarket generally favors POE oil because POE is compatible with both R-12 and R-134a and unlike PAG oil it will mix with mineral oil. Mineral oil, as a rule, should still be used in older R-12 systems.

SHOULD YOU USE AN ALTERNATIVE REFRIGERANT?

The use of alternative refrigerants in older R-12 vehicles will continue because in some cases there is no other option other than converting to R-134a. Vehicle manufacturers discourage using alternative refrigerants and recommend R-134a for retrofitting older R-12 systems.

DO NOT use any alternative refrigerant in a vehicle with a R-134a A/C system (most 1995 and newer vars and trucks). This is illegal and may cause cooling problems and/or compressor failure.

DO NOT use any alternative refrigerant in newer vehicles that have a R-1234yf A/C system. This is also illegal and may cause cooling problems and/or compressor failure.

To minimize the risk of refrigerant cross-contamination, the EPA requires that each type of refrigerant (including alternative blends) have unique service fittings (permanently installed) and proper labeling. The EPA also requires shops to use a separate dedicated recovery/recycling machine for R-12, R-134a and R-1234yf, plus one or more additional recovery only machines for any other refrigerants that might be used. For this reason, many shops choose to avoid blends. But fleets may find blends to be an acceptable alternative if they do not want to convert (or it would cost too much to convert) their vehicles over to R-134a.

To protect recycling equipment against cross-contamination or bad refrigerant, service facilities should use a refrigerant identifier to check every vehicle before it is serviced. An identifier can also help the shop monitor the quality of their recycled refrigerant as well as any virgin refrigerant that might be purchased.

The best advise is this: if you do not know what type of refrigerant is in your vehicle, take it to a shop that has a refrigerant identifier and have it checked. Intermixing different refrigerants can cause cooling problems as well as shorten the life of the A/C compressor.

REFRIGERANT CONTAMINATION ALERT!

As the use of alternative refrigerants grows, so does the risk of cross-contamination. A recent survey by the Florida EPA revealed some startling results. When they tested the refrigerant recovery tanks in about 100 shops, here is what they found:

Thirty-eight percent of the recovery tanks showed some type of contamination! Independent repair garages and service shops had the lowest rate of contamination, but it was still 32% (nearly one out of three). Used car dealers were the worst, with 71% of their recovery tanks (almost three out of four) showing signs of contamination.

Air contamination was the worst problem, being present in 22% of the tanks tested overall. But cross-contamination between R-12 and R-134a was also found in 15% of the tanks. The most cross-contamination (29%) was discovered in used car dealers.

RETROFIT TO r-134A OR NOT?

Use R-12 in all R-12 systems as long as it is available because R-12 provides the best cooling performance in these applications. There is no need to retrofit to R-134a or to use any other refrigerant as long as the system is cooling normally. But if your A/C system requires major repairs such as a new compressor or condenser, the cost to retrofit is justified.

Switching an older R-12 system to R-134a does not require a lot of modifications in most instances. Changing the accumulator or receiver-dryer, removing the old compressor oil and replacing the high pressure switch is generally all that is needed. For more information, consider purchasing the R134A RETROFIT GUIDE on this website.

OEM as well as aftermarket retrofit kits are now available for such conversions. But some vehicles (namely certain Japanese cars that have compressors with Viton compressor seals, or certain older Fords with compressors that can't handle higher head pressures or have small condensers) are not so easy to convert. Changing some of these vehicles over to R-134a requires extensive and expensive modifications. So for these applications an alternative refrigerant may be the best choice if R-12 is unavailable.

Down the road, a number of new alternative refrigerants have been developed that may replace R-134a. For more information about the changes that are coming and why these changes are being required, click here.

Click Here for info about A/C R134a Retrofit Guide

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Saturday 27 June 2015

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