AIR CONDITIONING PROBLEMS

How to Check Your Car's Air Conditioning System

You should check your car's A/C system BEFORE hot weather arrives to make sure it is working properly and blowing cold air.
 
 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. 


 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.
 

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.

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.

Troubleshoot Air Conditioning

A/C COOLING PROBLEM?

The most likely cause of an automotive air conditioner cooling problem is no refrigerant in the system. If the refrigerant has escaped past a leaky compressor or O-ring seal, leaked out of a pinhole in the evaporator or condenser, or seeped out through a leaky hose, the leak needs to be identified and repaired before the system is recharged.
On many systems, the compressor will not turn on if the refrigerant is low because the "low pressure safety switch" prevents the compressor clutch from engaging if system pressure is low. This protects the compressor from possible damage caused by a lack of lubrication.
One of the first things you should check, therefore, is compressor engagement. If the compressors magnetic clutch is not engaging when the A/C is turned on, the problem may be a blown fuse or a wiring problem. If the fuse is blown, replacing it may restore cooling temporarily. But the underlying reason for the fuse blowing in the first place needs to be identified and corrected to prevent the same thing from happening again.
If the magnetic clutch is receiving voltage but is not engaging the compressor, the clutch is defective and needs to be replaced. If there is any evidence of leakage around the compressor shaft seal, the seal should also be replaced.
If the clutch works but fails to turn the compressor (the belt may squeal in protest!), the compressor has seized and needs to be replaced.
Compressor failures are usually the result of loss of lubrication, which in turn may be due to low refrigerant in the system, a blockage (such as a plugged orifice tube which prevents refrigerant and oil from circulating to the compressor), loss of lubricant due to leaks or improper service procedures (not adding oil to the system to compensate for oil lost through leakage or component replacement), or use of the wrong type of lubricant.
R-12 systems require mineral oil while R-134a systems require various types of PAG oil or POE oil. Using mineral oil in a newer R-134a system can cause serious lubrication problems as can using the wrong grade (viscosity) of PAG oil. Always follow the vehicle or lubricant manufacturers compressor oil recommendations.
The next thing you should check when troubleshooting a no cooling problem is system pressure. For this, you need a set of A/C service gauges. Attach your service gauges to the high and low service fittings. If both the high and low side pressure gauges read low, the system is low and needs recharging. But before any refrigerant is added, check for leaks to find out where the refrigerant is going.
LABELS: AIR CONDITION