Skip to main content

The heart of your car’s A/C system

The compressor is a pump that moves refrigerant through your car’s air conditioning system. The refrigerant is carried by hoses and pipes from one component to another. Compressor designs vary, but they all essentially work the same way. 
The compressor is belt-driven by the engine through an electromagnetic clutch (although some hybrid vehicles use an electric motor to operate the compressor). The clutch allows the compressor to disengage when the A/C is switched off, or at times during A/C system operation when compressor function is not called for. The clutch usually receives its electrical signal from a component called a relay, which in turn, receives its activation signal, in most cases, from the fuel injection or engine control computer.  
Besides pumping the refrigerant, the compressor has another job; at a certain point in the system, it raises the pressure of the refrigerant from low to high, and as the refrigerant’s pressure goes up, so does its temperature. Raising the refrigerant’s pressure and temperature enables it to release the passenger compartment heat it absorbed while inside the evaporator. The heat release process takes place in the next component to be discussed, the condenser.
The compressor can somewhat be compared to the water pump in an engine cooling system:

  • The water pump circulates the engine coolant throughout the system. The coolant absorbs heat from the engine, and the water pump moves it to the radiator where it releases the heat to the atmosphere. It also circulates hot coolant through the heater core to warm the interior of the vehicle.


  • The compressor circulates the refrigerant through the system. The refrigerant absorbs the heat inside the vehicle while passing through the evaporator. The refrigerant is then passed on to the condenser, where it gives up the heat to the atmosphere.


Things that can go wrong with A/C compressors aka heart stoppers!

Compressors are generally reliable components, but can catastrophically fail due to a lack of lubrication, just like your car’s engine. Lubricating oil can leave the system if a refrigerant leak occurs, because the leaking refrigerant can carry lubricant out with it. Such a failure can cause the compressor to lock up (seize) or wear out prematurely. A catastrophically failing compressor can also load up the inside of the A/C system (particularly the condenser) with debris, usually small chips of metal.
A compressor can also fail because of too much oil in the system, which can cause its internal valves to break. Compressors themselves may also develop a refrigerant leak, which usually necessitates their replacement.
Compressors may also be damaged by things such as an overcharge of refrigerant, excessive amounts of air in the system, the use of the wrong refrigerant or lubricant, inadequate condenser airflow, or even engine cooling system problems. And of course, just like any other component that contains moving parts, compressors may sometimes fail simply due to wearing out or breakage.
Unlike in years past, with the exception of clutch replacement, compressors are not generally serviced in the repair shop any longer. They are usually replaced. Make sure to visit a professional service shop if your compressor goes bad.
When having your mobile A/C system professionally serviced, insist on proper repair procedures and quality replacement parts. Insist on recovery and recycling so that refrigerant can be reused and not released into the atmosphere.
You can E-mail us at or visit to find a Mobile Air Conditioning Society repair shop in your area. Visit to find out more about your car’s mobile A/C and engine cooling system.

0 responses to “The heart of your car’s A/C system”

  1. […] The heart of your car’s A/C system | Mobile Air … – Jul 08, 2010 · The compressor is a pump that moves refrigerant through your car’s air conditioning system. The refrigerant is carried by hoses and pipes from one …… […]

Leave a Reply

Your email address will not be published. Required fields are marked *