Auto Repair Help
by Mark Davidson

The A/C compressor is mounted on the engine and driven by a belt attached to the crankshaft pulley. Components include an electromagnetic clutch coil, compressor clutch pulley, compressor drive plate and compressor assembly. Refer to the correct auto repair book to get the schematics of these components and their connections. The electromagnetic clutch is operated by electrical current supplied to the clutch. When energized, it becomes a magnet locking the compressor drive plate to the clutch pulley. The compressor drive plate in turn rotates the shaft of the compressor. The compressor drive shaft rotates the internal pistons of the compressor that pressurizes and circulates the refrigerant throughout the system.

The air conditioning evaporator is installed in the HVAC module. The evaporator consists of a series of interconnected finned tubes set in cubic arrangement with an inlet and outlet fitting. High pressure liquid refrigerant is metered into the evaporator using a refrigerant flow control device, where it is changed to a low pressure gas inside the evaporator. The process of the high pressure liquid refrigerant changing to a low pressure gas causes heat to be removed from the air blown across the evaporator. As the air is cooled, the moisture content of the air condenses into water on the evaporator fins. The water is then drained out of the HVAC module to the outside of the vehicle by the evaporator drain tube.

The air conditioning condenser is placed in front of the radiator at the front of the vehicle. It is constructed of finned aluminum tubing and resembles a thin radiator. The condenser is used to change high pressure refrigerant gas flowing from the compressor, into a high pressure liquid refrigerant. This is accomplished by transferring heat to the air flowing through the condenser. As the heat is removed from the refrigerant, it condenses to a liquid. Air flow across the condenser is vital to the correct operation of the air conditioning system. If the air flow is inadequate, system pressures can rise dramatically causing poor air conditioning performance and possible system damage. At stops and at low speeds, a fan is used to provide air flow across the condenser. When the vehicle is moving at speeds above 45 mph, enough air will flow through the condenser to properly cool the refrigerant. Most rear wheel drive vehicles use an engine driven cooling fan to draw air across the condenser. Because of their design, front wheel drive vehicles are not able to use an engine driven cooling fan. Instead, an electric fan is used for condenser air flow. The cooling fan operation is normally controlled through a relay. Depending on the system used, the relay can be operated by refrigerant pressure sensors, vehicle control modules or to coincide with air conditioning compressor operation.

(Mark gave up on sports when the Browns left Cleveland and now spends his Sundays working under a shade tree in the back yard tuning his son’s soap box derby car.)

5 responses to “Ac Compressor”

  1. matt simon says:

    I have a 1979 Pontiac trans am with a 403 olds motor in it. My a/c compressor has broken. I don’t know what the right term is. Do you repair, reseal, or remanufacture a/c compressors? If so, how much do you charge and how long would it take? If you do, I would mail my a/c compressor to you to fix. Please let me know. Thank you

  2. Mr Sames says:

    AC compressor are doing a great job to provide the exact amount of pressure of the air for cooling.

  3. Air Tool Guy says:

    Hey, any idea on what is the best compressor brands I should have? Looking around but not sure what should I buy

    • Zach says:

      I usually recommend the “California Air Tools 5510SE”. It’s a great all around compressor for basic needs. You get around 3.10 CFM at 40 PSI.

  4. Addy Brown says:

    The air conditioning evaporator is installed in the HVAC module. The evaporator consists of a series of interconnected finned tubes set in cubic arrangement with an inlet and outlet fitting.

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