Car Air Conditioning Compressor Noise?

We often get asked if we can supply a new car air conditioning compressor (aircon pump) clutch plate, or pulley as the unit on the car is noisy. In a word, no we can’t. But there is a reason for that. We could supply those parts, in fact we replace those parts when we rebuild a compressor if that’s what the customer wants, but, you should never just change the clutch plate or pulley.

A noisy compressor clutch plate / pulley is a symptom of a problem with the cars’ aircon. Not the cause. So merely replacing the noisy parts will not solve the problem. Well, it will for a short time, but then the same thing will happen again unless the ’cause’ of the problem is found, and rectified.

Information from Denso, one of the biggest car aircon compressor manufacturers in the World details a whole list of possible causes of a noisy aircon clutch plate or pulley:

  • If the engine is not running smoothly, because of poor injection (diesel engines only) then this causes extra torque through the belts and the plate fails, or if the clutch on the alternator fails the same thing happens.
  • Seized or too high slip torque of free run pulley’s. Alternators have the so called free run pulleys and when these are seized or the free run slip torque is too high, the limiter will break due to negative force. (Belt movement). German car makers do advice to replace the pulley when compressor is replaced.
  • Too low force of Automatic belt tensioner. This will result in too much belt movement and can cause limiter to break.
  • Liquid lock. Too much refrigerant or too much compressor oil causing too much liquid in the compressor cylinders. This does not always mean the compressor is stuck, but does have a too high rotation torque caused by too much refrigerant or too much oil. Have your car properly aircon serviced, recharged to check this is not the problem.
  • Use of incorrect compressor oil. Mixing of different type of oils still happens a lot. POE or POA oils do NOT mix with the PAG 46 oil used by DENSO and can cause different problems.
  • Mixing POA and PAG 46 causes kind of paraffin flakes which increases friction and can even cause cylinder lock (like liquid lock) and blockage of refrigerant cycle / Compressor main control valve.
  • Mixing POE and PAG 46 will reduce oil film between cylinder and pistons resulting in higher friction. When systems are flushed using flushing agents containing chloride, kind of clear wax is created resulting in piston lock similar to that of liquid lock.
  • Incorrect viscosity PAG 46 –> PAG 100 will reduce oil film between rotating / sliding parts increasing wear and friction.

So as you can see, the car aircon specialist servicing your car, for example our guys at Cool Car need to check all of the above before replacing any aircon component, otherwise any compressor problems, will simply re-occur.

Of course if you do need a new aircon compressor, then of course we can help with all makes and models from our stock of over 25,000 car aircon parts, delivered free next working day.

Simon Parker

Director & Partner of Cool Car Limited. Owners of and