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Showing posts with label AC repair. Show all posts
Showing posts with label AC repair. Show all posts

Saturday 27 June 2015

How To Recharge Your Car's Air Conditioner

 Car's Air Conditioner Recharge Procedure


a/c recharging


LOW REFRIGERANT

If your air conditioner is not cooling well because the system is low on refrigerant, recharging the system with refrigerant should restore normal operation. This can usually be done with a few cans of refrigerant and a simple service hose connection.

A/C RECHARGING PRECAUTIONS

First, wear safety glasses to protect your eyes. Also avoid skin contact with refrigerant. The chilling effect of spilled refrigerant can cause instant frostbite on bare skin or eyes!

WHAT TYPE OF REFRIGERANT?

Next, you need to figure out what type of refrigerant your vehicle requires:
On 1995 and newer passenger cars and light trucks, the correct refrigerant is R134a. DO NOT use any other type of refrigerant.

On most 1994 and older passenger cars and light trucks, the original refrigerant was R12. R12 is no longer available to do-it-yourselfers and is very expensive. When older vehicles with R12 A/C systems need refrigerant, they can be refilled with recycled R12 from other older cars (this requires taking your car to a repair shop for professional service), or with some alternative refrigerant other than R12, or with R134a (which requires certain modifications).
CAUTION: Mixing different types of refrigerants is NOT recommended. Use the same type of refrigerant that is already in the system unless you are converting an older R12 system to R134a or another refrigerant.
WARNING: Flammable refrigerants are illegal. DO NOT use any type of flammable refrigerant (propane, butane or flammable hydrocarbons).
For more information, see Flammable Refrigerants
Click here for more information about retrofitting older vehicles with R12 A/C systems to R134a.

LOCATE THE SERVICE FITTINGS

Next, you need to locate the service fittings on the A/C system. There are two: a LOW side fitting and a HIGH side fitting. The LOW side fitting is usually located on the suction hose or line that goes from the accumulator to the compressor. The HIGH side fitting is located on the line that goes from the compressor to the condenser.
ac low and high side service fittings





On older R12 systems, the LOW and HIGH pressure service fittings are screw-type schrader valves. On newer R134a systems, the LOW and HIGH side service fittings are quick-connect style fittings. The LOW pressure fitting is SMALLER than the HIGH pressure fitting.

air conditioning refrigerant can hookup for recharging

AIR CONDITIONING RECHARGE PROCEDURE

1. Connect the recharge service hose and valve to a can of refrigerant.

2. Turn the valve on the service hose to puncture the top of the can.

3. SLOWLY turn the valve back out to release a small amount of refrigerant into the hose. This will blow air out of the hose (which you do not want in your A/C system). 

4. Close the valve so no more refrigerant escapes, then quickly connect the other end of the service hose to the LOW pressure service fitting on the A/C system.
CAUTION: DO NOT connect a can of refrigerant to the HIGH side service fitting. The operating pressure inside the A/C system when it is running may exceed the burst strength of the can, causing the can to explode! This should be impossible to do because the service hose for recharging the A/C system will only fit the smaller LOW pressure service fitting. Even so, you should be aware of the danger.

5. Hold the can UPRIGHT so no refrigerant liquid enters the service hose. You only want VAPOR to be pulled into the A/C system (the compressor may be damaged if it sucks in a big dose of liquid!).

6. OPTIONAL BUT HIGHLY RECOMMENDED: You should use a gauge to monitor the recharging process. Though not absolutely necessary, a gauge will help you recharge your A/C system more accurately, and reduce the chance of undercharging or overcharging (either of which will reduce cooling performance).

A high pressure A/C gauge can be connected to the HIGH pressure service fitting, or a low pressure A/C gauge to the LOW pressure service fitting, or gauges can be attached to both fittings (that is what professional technicians do).

NOTE: Some DIY recharging kits include a low pressure gauge on the service hose or on a trigger-grip style can dispenser.

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7. Start the engine and turn the A/C on MAX/HIGH.

8. NOTE: The compressor may not engage if the system is too low on refrigerant. The low pressure cutout switch will prevent the compressor from running if the system is too low on refrigerant (this is done to protect the compressor from damage due to a lack of proper lubrication). The compressor must be running to suck refrigerant through the service hose into the system. So if it is not engaging when you turn the A/C on, you may have to supply battery voltage directly to the compressor clutch using a fused jumper wire. Look for a single wire connector near the front of the compressor, unplug it and hook up a jumper wire to the battery POSITIVE terminal. This should cause the clutch to engage and the compressor to run.

9. OPEN the valve on the service hose so refrigerant vapor will flow from the can into the A/C system. It may take up to 10 minutes or more per can to suck all of the refrigerant out of the can into the A/C system. Feel the air coming out of the ducts inside the vehicle. It should be getting colder.

10. If you are using a high or low pressure gauge (or both) to monitor recharging, look at the gauge(s). 

LOW pressure gauge: When the reading is between 25 and 40 psi with the A/C running, STOP. The system is fully charged and should be cooling normally. DO NOT add any more refrigerant. If the gauge is over 50 psi, you have overcharged the system with too much refrigerant.

High pressure gauge: When the reading gets up around 200 to 225 psi (R12), or225 to 250 psi (R134a),STOP. The system is fully charged and should be cooling normally. DO NOT add any more refrigerant.

NOTE: The high and low pressure readings will vary depending on the system and ambient temperatures (higher temperatures cause higher system pressure readings).

Refer to the vehicle manufacturer specifications for normal system operating pressures, and the total refrigerant capacity of the system. Most newer passenger car A/C systems do not hold much refrigerant (only 14 to 28 oz.), so you don't want to add too much if the system is low. One can of R134a typically holds 12 oz. of refrigerant.

11. If the system needs more refrigerant after adding one can, you can add a second can. CLOSE the valve on the service hose, then disconnect the hose from the empty can, screw a new can onto the service hose valve, turn the valve to puncture the new can, then turn the valve all the way back out again so refrigerant can flow through the hose into the A/C system.

When you have finished, turn the engine off. CLOSE the valve on the can of refrigerant before disconnecting the service hose from the LOW pressure fitting (in case there is any refrigerant left in the can). Don't vent any left over refrigerant from the can. Leave the service hose attached to the can with the valve closed so you can save the refrigerant for a future recharge.

Remember to replace the plastic caps over the service fittings, and remove the jumper wire from the compressor if you had to jump it to make it run.
IF THE A/C SYSTEM STOPS BLOWING COLD AIR AFTER A FEW DAYS, WEEKS OR MONTHS
If your A/C stops blowing cold air several days, weeks or months after you recharged it, it means the system has a leak and the refrigerant is escaping. You should add some leak detection dye to the system to find the leak. The leak should then be repaired before the system is recharged again, otherwise you are just wasting your time recharging the system over and over again.


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Auto Air Conditioner Blowing Warm Air, Not Cooling

Auto Air Conditioner Blowing Warm Air, Not Cooling


Is you car's air conditioner blowing warm air only and no cool air? Your A/C cooling problem could be caused by any of the following:

Your A/C system may have lost its charge of refrigerant. This is probably the most common cause of a no cooling problem. Another possible cause of no cooling may be that your A/C compressor is not be engaging when you turn on the A/C. This can be caused by an electrical fault in the A/C compressor circuit or the magnetic clutch that drives the compressor. Another cause could be an internal obstruction inside the refrigerant circuit that is preventing refrigerant from circulating inside the A/C system. Another possibility might be a blend air door inside the HVAC unit that is stuck in the HEAT position and is preventing air from flowing through the A/C evaporator.

car a/c ducts


Compressor Checks

 Start with the compressor. Does it engage when you turn on the A/C?
If so, the compressor is working and the A/C system probably contains enough refrigerant to make cold air, so the problem is inside the HVAC unit. Replace the motor that controls the blend air door (this is a difficult job and best left to a professional since it involves tearing apart the HVAC unit -- about an 8 to 10 hour job!).
If the compressor does not engage when you turn on the A/C, see if it will run by jumping the compressor clutch wire directly to the battery (use a fused jumper wire). If the compressor works when you jump it, and the A/C blows cold air, the system contains refrigerant and the fault is likely a bad A/C compressor clutch relay or a bad clutch cycling switch or pressure switch.
If the compressor does not engage when you jump it, the problem is a bad compressor clutch.
If the clutch engages but the compressor does not turn (the belt will start to slip and squeal), the compressor is locked up and you need a new compressor.
If the compressor clutch engages and turns the compressor, but the A/C still does not blow cold air, the system is probably low on refrigerant and needs to be recharged.

Refrigerant Checks

 Connect an A/C pressure gauge to the HIGH SIDE service port (located in the high pressure hose that runs between the compressor and the condenser in the front of the engine compartment). The gauge will tell you if there is any pressure in the system. Simply depressing the service fitting valve with a small screwdriver to see if any refrigerant squirts out is NOT an accurate check because it tell you how much pressure is in the system. It may still have some pressure but not enough to trip the low pressure safety switch so the compressor will engage.
If your A/C system is low or out of refrigerant, check for leaks, then have the A/C system vacuum purged to remove air. After the air is out, it can be recharged with the specified amount of refrigerant. It is important to get any air out as this will reduce cooling efficiency and may make the compressor noisy.

A/C System Functional Checks

 If the refrigeration circuit seems to be working (refrigerant in the system, compressor running and building pressure), but there is still no cooling, the problem might be an obstruction in the orifice tube (located in the high pressure hose between the condenser in the front of the radiator, and the evaporator located in the passenger compartment). A blockage here will prevent the refrigerant from entering the evaporator or recirculating through the refrigeration circuit.
If the orifice tube is plugged, the high side pressure reading will be lower than normal, and the low side reading will also be lower than normal because no refrigerant is circulating through the system.
 If the refrigeration circuit seems to be functioning normally (compressor running, frost or condensation on the high pressure line from the condenser to the evaporator), but no cool air is blowing out of the ducts inside the car (and the blower is working), the fault is likely a BLEND AIR door that is stuck in the HEAT position, or possibly a badly clogged cabin air filter that is restricting airflow. Another possibility would be a fault in the automatic climate control system such as a ad interior temperature sensor or control module.
My advice to you if you know nothing about A/C service is to find a repair shop that specializes in A/C repairs and let them diagnose and repair your air conditioning cooling problem. Today's A/C systems with automatic climate control are very complex and require special tools and know-how to diagnose and repair.


Air conditioning diagnostic chart


This air conditioning diagnostic chart shows typical Low and High side gauge readings, and duct temperatures for common A/C cooling problems.

A/C Gauge Readings

To determine the HIGH SIDE and LOW SIDE pressures inside your vehicle's air conditioning system, you need an A/C Gauge Set. The Gauge Set must be connected to the A/C service ports on vehicle to read the pressures while the system is running.
With the engine OFF, connect the A/C Gauge Set High Pressure Hose (the one with the larger coupler fitting) to the High Side service port (usually located in the compressor output line that goes from the compressor to the condenser). Connect the Low Pressure Hose (the one with the smaller coupling) to the Low Side Service port (usually located on the accumulator, or on the suction hose that goes from the evaporator to the compressor).
Start the engine, turn on the A/C to MAX, and rev the engine to 2000 RPM. Hold the engine speed and note the High and Low side pressure gauge readings.
NOTE: High and Low side pressure readings will vary with ambient temperature and humidity. The higher the temperature and/or humidity, the higher the gauge readings.
With late model R134a systems, good high pressure readings should range from 150 to 220 PSI at 80 degrees F, 170 to 250 PSI at 90 degrees F, and 195 to 280 PSI at 100 degrees F.
A High side pressure reading of less than 150 PSI indicates a low charge or a compressor problem. A high pressure reading over 300 PSI would indicate an overcharge condition (too much refrigerant in system) or a restriction in the high side.
Good low pressure readings with R134a should usually be in the 30 to 35 PSI range. If higher, there may be a low side restriction. If the reading is lower, the system may be low on refrigerant.
With older R12 A/C systems (1994 model year vehicles an older that have NOT been retrofitted to R134a), the HIGH side pressure readings will typically be 150 to 185 PSI at 80 degrees F, 175 to 205 PSI at 90 degrees F, and 200 to 250 PSI at 100 degrees F. Normal LOW side readings with R12 should be around 20 to 30 PSI for an expansion valve system, or 15 to 40 PSI for an orifice tube system.


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How to Check Your Car's Air Conditioning System

Car's Air Conditioning System Inspection & Checking


automotive air conditioning service

You should check your car's A/C system BEFORE hot weather arrives to make sure it is working properly and blowing cold air. The following tips on how to check your car's air conditioning system has been provided by the Mobile Air Conditioning Society (MACS):

Note: Always be extremely careful any time you are under the hood while the engine is running. Stay away from all rotating components with your hands, clothing, and hair, and always wear eye protection around a running engine.

 1. With the engine running, does the compressor clutch engage when the A/C is switched on? If it does not, this usually indicates a low (or empty) refrigerant condition, or an electrical problem. Also, listen for rapid clicking or cycling noises at the compressor when the A/C is switched on. If this is happening, it could also indicate low refrigerant or some other problems. Have it checked by your service technician. (Note: Some A/C systems prevent compressor clutch engagement in low temperatures, typically at or below 40° F.)


 2. Is the A/C system blowing cold air? Luke warm air or air that is barely cooled at all could indicate a low refrigerant charge in the A/C system. Pressure gauges can be used to check the refrigerant charge. If low, add refrigerant to bring the system up to full charge. See How To Recharge Your Car's Air Conditioner for more information on how to add refrigerant.


 3. With the engine running and the A/C switched off, listen for knocking or rumbling sounds in the vicinity of the compressor. These could indicate a failing compressor clutch, and/or loose mounting hardware.


 4. Are A/C component mounting bolts in place and tightly secured? Nothing loose or rattling around?


 5. Are caps installed on the A/C system service ports? This keeps out dirt, and also provides a seal for refrigerant.


 6. Check all belts for cracks, wear, and glazing. Have them replaced at the first sign of any of these conditions. Also, check for belts that vibrate while the engine is running and the A/C is on. This may indicate a belt that needs to be tightened, or a defective automatic belt tensioner.


 7. Examine all A/C and cooling system hoses for cuts, abrasion, weak spots, and signs of leakage. Leakage from A/C system hoses is often indicated by an accumulation of dirt and oil, particularly at connections and fittings.


 8. Make sure the condenser (in front of the radiator) is free of any obstructions, such as leaves or insects. This could reduce airflow, resulting in reduced A/C performance. You can rinse the condenser clean with a garden hose.

More Air Conditioning Articles:

MACS Recommended A/C Service Procedures (PDF file)

A/C Cooling Problem: Blows Warm Air Only No Cool Air

Troubleshooting Air Conditioning Problems

Troubleshoot Automatic Climate Control 

Troubleshooting A/C Cooling Problems with Temperature

Cooling Fan (electric)

Cooling Fan Relay Problems

How To Recharge Your Car's Air Conditioner

Refrigerant Contamination 

Alternative Refrigerants for R-12

New Automotive Refrigerants 
California proposes ban on R134a sales to motorists

Information about Retrofitting older vehicles with R-12 A/C systems to R-134a

A/C Compressor Failures

A/C Condenser Flushing
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