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.