How to Troubleshoot a Noisy Air Conditioner Clutch

The parts under the hood of a car.

In any auto air conditioning system, there are several key parts. These include the air conditioner clutch assembly, heat exchanger, compressor, drive belts, and pumps. This guide will help you diagnose the problem when you start hearing strange noises.

How It Works

Operationally, here is what happens when you engage your car’s air conditioning system:

  • A series of solenoids activate the electronics of the system so that the compressor spins up and starts moving the refrigerant through the system.
  • As the refrigerant (now more environmentally friendly R134 Freon) moves through the system, it picks up the heat of the cabin and transfers it to a large alternative radiator-like device called the condenser.
  • Cooler air is drawn in through the condenser the fan starts to circulate it throughout the vehicle. The compressor is the heart of the system.
  • The compressor works only when it is engaged to the engine and that engagement is through the air conditioner clutch.

That, in simple detail describes how the system works. Normally, you should hear or feel nothing when the air conditioner is working except the cold air coming from your car’s heating/cooling ducts. There are times, though, where you might hear a squealing noise when you engage the air conditioning system. This could either be the air conditioning clutch or the serpentine belt slipping.


car dashboard

  • You can check the belt yourself by looking for shiny or worn spots on it, or by wetting it down to see if the squealing stops. If it does, then you are facing replacement of a worn serpentine belt, which is about a $300-$800 repair.
  • If the squealing continues, it could indicate the air conditioner clutch is out of alignment or, worse, going bad. If this is the case, then you can try to do the repair yourself — although, given today’s EPA rules for refrigerant recovery, it’s probably best to let a professional mechanic handle it.
  • Another noise you might hear from the air conditioner clutch is a heavy thunk when you engage the air. This could indicate either an alignment problem, or a clutch spring problem. It should be checked out by a professional.
  • Still another air conditioner clutch condition that you might feel, more than hear, is a slight vibration when the air conditioner clutch disengages when you are idling at a light or if your vehicle has reached the temperature you want. Again, this is something that should be checked out by a professional.

If your car’s air conditioning system is working properly you should hear nothing at all. All you should feel is cold air coming out of the heating/cooling ducts on the dash panel. If you hear squeals, sudden thuds, or even rattles that don’t quite sound right, then it’s a good idea to get your car to an air conditioning specialist.

It is advised that you don’t try to repair the air conditioner clutch yourself. This is because it is a very complicated device that involves proper shimming, to set it correctly. It also involves the proper handling of the refrigerant according to EPA standards.