Getting the right A/C Compressor
by Staff Writer

The compressor, a belt driven pump found in the engine, is commonly referred to as the heart of the system for many reasons. One main reason is that when it fails you know that something is wrong with your overall a/c system. Just as when a heart fails, the body feels it, when a compressor locks up or the clutch seizes, the automobile is affected. The compressor is made up of many smaller components, one large component is the electro-magnetic clutch, which engages and disengages the compressor once power is/is not provided via the vehicle. The complete compressor with clutch is responsible for compressing and transferring refrigerant gas. The movement of refrigerant passes heat from the internal of the vehicle to the external.

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The auto a/c system has two sides, a low-pressure side and high-pressure side, also called the discharge and suction. The low-pressure side connects to the inlet (suction) of the compressor and the high-pressure side connects to the outlet (discharge).The compressor acting as a pump, on the intake side takes in low-pressure gas coming from the evaporator or sometimes the accumulator or receiver/drier and compresses it into a high-pressure hot gas sent to the condenser. From there, it transfers heat that was absorbed from the inside of the vehicle.The a/c compressor compresses freon into a high pressure and temperature gas. The gas is then sent to the condenser to remove heat. As this temperature is typically higher than the outside temperature, heat transfers to the outside air. This gas is then condensed back to a high pressure liquid. The liquid is sent to a restriction in the system (ie. orifice tube or expansion device) and this lowers the pressure. The liquid then boils and vaporizes, in other words evaporates. The cycle is able to repeat in this low pressure gas state. A benefit to the compressor circulating the refrigerant is that it provides lubrication to the main parts of the a/c system.

Please also note that the compressor should be properly lubricated prior to installation in the vehicle. The oils vary from mineral to Pag oil, and the viscosity is also vital. For optimal performance you would want your a/c professional to look at the approximate ounces and appropriate viscosity. Some seals and gaskes may not work with certain oils.

Clues that you may need a new compressor include:1) Poor cooling or no cooling in vehicle2) Noise coming from the unit under the dash3) A seized compressor causing a belt slip4) Burning smell coming from clutchUsual suspects which contribute to compressor failure:1) Low refrigerant2) Lack of or incorrect lubricant3) Particles of debris such as metal chips in the system causing internal deterioration

It is important that an a/c professional check your air conditioning system at least once a year. Since the a/c system also helps defrost your windshield during the cool season, it is not suggested to only have it checked in the summertime. Keep the refrigerant filled and your system won't get damaged due to poor lubrication flow. The a/c professional should also use the correct refrigerant and oil to keep it from performing poorly. Last but not least, it is important the technician follow each compressor manufacturer's unique diagnostic procedure and not take shortcuts. Know the system, don't just replace the compressor but correct the root cause of the initial failure.

Once the refrigerant is drawn into the suction side, it is compressed and sent to the a/c condenser, where it can then transfer the heat that is absorbed from the inside of the vehicle.

The a/c compressor compresses freon into a high pressure (and since temperature and pressure are relative), high temperature gas which is then sent to the condenser for the process of removing the heat. The fact that this temperature is greater than the outside temperature allows the heat to transfer to the outside air. This then causes the "gaseous" freon to "condense" back to a high pressure liquid. This high pressure liquid is then sent to the restriction in the system (that being an orifice, or a valve of some kind) which lowers the pressure causing the liquid to boil and vaporize (thus the term "evaporator"). It is then in this low pressure gas state that it is capable of absorbing the heat from inside the vehicle and sent back to the compressor for the cycle to repeat itself.

The compressor is lubricated with special oil. It is very important to use the correct oil to the compressor and system. Some seals and gaskets may not work with some oils.

Description: The air conditioning (A/C) electro-magnetic clutch mounts to the front of the air conditioning compressor and electrically engages and disengages according to commands from the A/C system. A/C Compressor designs may vary from one manufacturer to the next as to internal design and components. The A/C system is divided into two sides: high-pressure and low-pressure. The low-pressure side connects to the inlet of the compressor and the high-pressure side connects to the outlet, or discharge, of the compressor.

Purpose: Upon command, the A/C clutch energizes and locks the clutch to the compressor. Once engaged, a serpentine belt or V-belt from the engine drives the A/C compressor. The compressor?s main job is to pump refrigerant through the system so it can remove heat from the interior of the vehicle. Circulation of refrigerant also provides a secondary benefit? It moves refrigerant oil throughout the system, providing lubrication to key parts of the system.

Maintenance Tips / Suggestions: Symptoms of a bad compressor or compressor clutch include poor or no cooling, and a noisy or seized compressor. Have your vehicle?s air conditioning system checked yearly by a professional technician. The A/C system also operates when the climate control system is in the defroster mode to remove moisture from the interior, so A/C is more than a summertime creature comfort. Operating an A/C system low on refrigerant not only results in poor cooling, it can also damage the system due to poor lubrication flow. Make sure that the technician servicing your car uses the correct refrigerant and refrigerant oil. Use of the wrong refrigerant or oil can reduce system performance or even cause damage.

Vehicles are found to have primarily three different types of air conditioning systems. While each of the three types differ, the concept and design are very similar to one another.