Photograph of a burned out old air conditioning compressor condenser unit How to replace a burned-out air conditioning or heat pump compressor

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Air conditioner or heat pump compressor motor replacement outline: this air conditioning repair article describes the basic steps involved in replacing a burned out air conditioner compressor.

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What is Involved in Air Conditioner Compressor Replacement

Replacing an air conditioner compressor is a job for a trained service technician. Not only is the compressor motor often the most costly part in the system, but it is not a simple "bolt-in" replacement. The service technician will:

  • Confirm that the compressor has failed and needs replacement. Note that a short-cycling or humming compressor may be due to other system problems - it's not always the case that the motor is actually seized.
    BURNED-OUT COMPRESSOR - how to determine that the compresor motor is burned out or seized
    HARD STARTING COMPRESSOR MOTORS - sometimes a start capacitor or relay replacement are all that's needed
    HVAC NOISE group 3 - where humming compressor noises are discussed
  • Identify the compressor model and capacity so that a proper replacement can be obtained
  • Shut down the air conditioning system, including turning off electrical power
  • Remove all refrigerant from the system. Modern procedures require that the refrigerant be captured rather than released to the environment in order to reduce environmental pollutants
  • If the air conditioner system used a now-obsolete refrigerant such as R11 or R22, a the new compressor will be one designed to use a new, approved refrigerant and other changes may be needed to the system to accommodate this change, such as changes in thermal-expansion valves, coils, or other components. Not all components need replacement, however; ducts and blower assemblies, for example, are retained.
  • The refrigerant lines are cut and the old compressor is removed.
  • The new compressor is installed in place in the compressor/condenser unit (usually all of this equipment is located outside), and its refrigerant lines are connected (usually silver soldering) to the existing refrigerant lines.

    New coils or other controls may need to be cut out and replaced if the refrigerant is being changed too.
  • A compressor motor burn-out filter is installed, possibly two of them on both the low and high side refrigerant lines at the compressor/condenser unit. This special HVAC compressor burnout dryer / filter may be installed on the refrigerant line(s) to provide extra debris and moisture and oil filtering capacity to protect the new equipment from debris clogging.

    Capillary tubes and TEVs as well as coils and compressors are vulnerable to damage or clogging from debris, stray oil, or water in the refrigerant piping system.
  • A vacuum is pulled on the entire system both to evacuate all air from the refrigerant lines and compressor and to check for leaks in the system. Air contamination, if allowed to mix with the new refrigerant would change its operating characteristics and would prevent proper operation.
  • Any water or moisture in the system is also removed and as we noted above, during re-connection of the refrigerant piping the technician may install a compressor burn-out filter-drier in the system to remove any trace moisture that remains behind after reassembly.
  • Refrigerant is added to the system at the proper charge amount. Residential air conditioner systems, unlike commercial units, use a hermetically sealed compressor motor and there is no separate receiver to hold a large refrigerant charge, so the charge must be measured precisely (including temperature, pressure, and volume during charging) for the system to work properly. Both overcharging and under-charging refrigerants will lead to improper system operation.
  • The air conditioning system, with its new compressor installed, will be re-started and checked for proper operation


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REPLACING A COMPRESSOR at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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