Air-conditioning systems on vehicles can help make a ride in the heat of summer more enjoyable as cold air comes pouring out the interior air vents. A failed air conditioning compressor, however, will cause the comfort of having cold air to cease. A problem with your air conditioning is not necessarily an indication that the compressor has failed, but there are some signs that can indicate that the compressor is problematic.
No Cold Air
Perhaps the most obvious symptom of a failed air conditioning compressor is the absence of cold air. All air conditioning systems take some time to cool a vehicle's interior, but if after a significant amount of time has passed you feel no cold air coming out of the vehicle's air vents this could point to the air compressor not operating correctly.
Lubricant or Refrigerant Leaks
An air-conditioning compressor requires lubrication just as the engine does, or else metal-on-metal contact will occur. The loss of lubrication will eventually lead to the compressor failing as it seizes from the excessive contact. Even with proper lubrication, a refrigerant leak can also lead to the compressor failing. The compressor generates a high amount of heat as it operates, and so it relies on the refrigerant not only to generate cold air for the occupants of the vehicle but to also cool off the compressor.
Like engines, air-conditioning compressors in different vehicles make varying degrees of noise when they operate. If you know your vehicle well enough, you should be able to tell if the compressor is making excessive noise such as squealing or loud knocking. These noises can indicate metal on metal contact as well as problems with air flow, which may be severe enough that the compressor needs to be replaced.