Troubleshooting Your Auto Air Compressor

If your car’s air conditioning system isn’t working as it should, there might be a problem with your auto air compressor. The AC system relies on the air compressor to pressurize the system’s Freon, which acts as a refrigerant to cool the air. When the air compressor isn’t functioning correctly, the air conditioning won’t work or will be ineffective, leaving you to drive in a hot, stifling car interior. Luckily, many air compressor issues are solved fairly easily and cheaply if you know what to look for; many of these problems create specific noises or other warning signs. Here are some common problems that may arise with your car’s AC compressor.

Listen for a Small Scraping Noise When the Compressor is Turned On

While the car is idling, turn on the air conditioner. If you hear a small scraping or tinny noise, turn the air off to see if the sound continues. If the sound is only present when the air conditioner is on, there is probably a problem with the clutch. You can usually replace this without dismounting the compressor from the engine.

Don’t Use the Air Conditioner if You Hear a Loud Knocking Sound

If operating the air conditioning system creates a loud clunking or knocking noise that goes away when you turn the air off, stop use of the AC system immediately. The clunking noise is a sign that the compressor is near the end of its life and is breaking apart. The pieces that are loose or have broken off making a knocking sound as they hit against the other parts of the system. Continued use of the AC under these conditions will cause more damage to the system, which may cause enough damage that you will need to replace the whole system.

Use Air Conditioning Gauges to Check Pressure

If the air that comes out of the vents isn’t cool, use air conditioning gauges to check the compressor. The pressure should be between 25 and 40 pounds on the blue side and between 210 and 250 pounds on the red side. If both numbers are lower than the minimum limits, it is an indication that the AC system needs charging. If the red side pressure is over 250 pounds but the blue side is normal, there may be a blockage somewhere within the system, such as in the orifice tube or expansion valve. If the red side is lower than 210 pounds and the blue side is higher than 40 pounds, you will probably need to replace the compressor altogether.

Check for Faulty Switches or Wiring

Sometimes the problem with a malfunctioning AC system is in the electrical wiring between the switch on the dash and the compressor. This is probably the case if you spot any broken or worn down wires. There could also be a problem with the pressure cycling switch at the compressor. You can check for problems here by using the pressure gauges to see if the pressure on both the blue and the red sides are within normal ranges.

Check for a Leak

Another issue that can affect the AC’s performance is leakage. The Freon, or refrigerant, that runs through the system can leak out of the compressor or through a gap in the hosing between the various components of the system. Try to inspect the system for leaks or stains. If you can’t find anything, you can add leak detecting dye to the system to help you spot the weak or faulty area.

Operating a car’s air conditioning system with a faulty air compressor can cause big problems. Although some problems may be small and mostly harmless, others can ruin your entire air conditioning system, which will be costly to repair. If your car’s AC is making noises or sending out uncooled air, you can try to diagnose the problem to determine how to fix it. If in doubt, it’s best to avoid using the AC until you can get a diagnosis for what is wrong with the compressor.