How to Diagnose an Air-Conditioning Problem With Your Car

Written by alibaster smith
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Your car's air-conditioning system works by compressing a refrigerant vapour (R-134A after 1996) under high pressure and heat. As it moves through the condenser, the refrigerant turns to liquid. Next stop is the dryer, where it's stored and excess moisture is removed. Still under pressure, the refrigerant liquid then moves through an expansion valve, where it returns to vapour form. Last, the vapour enters the evaporator, where it comes in contact with cabin air and sucks the heat out. Fans blow the cold air around the cabin. When your system is not working properly, you need to diagnose the problem so you can fix the right components.

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  1. 1

    Turn the A/C setting to the coldest setting and turn the fan on "high."

  2. 2

    Listen for the compressor to start. If you don't hear a "hum" when you turn on the A/C and a subsequent and temporary drop in the RPMs on your car, then the compressor has failed and needs to be replaced.

  3. 3

    Check to make sure the fan is working. If you set the fan speed to "high" and no air comes out, the problem is with the fan motor. You'll need to have this replaced.

  4. 4

    Wait a few minutes for cold air to start circulating into the cabin. If cold air is not blowing out of the vents, but you do have air coming out, then the problem indicates there is no more refrigerant in your system. You'll need to have the A/C system recharged with refrigerant by a mechanic. If the air is cool, but not cold, on the coldest setting, this can indicate a problem with the evaporator or condenser. Your A/C system will need to be serviced by a mechanic.

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