What causes A/C compressor slugging?

Written by andrea stein
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What causes A/C compressor slugging?
Air conditioner compressor slugging results from refrigerant flooding. (window air conditioner image by Aaron Kohr from Fotolia.com)

Air conditioning (A/C) compressors compress refrigerant by reducing its volume. Compressor operation can lead to slugging, which can damage a compressor or cause it to fail.


A/C compressor slugging refers to refrigerant flooding in the compressor. This flooding often results from an overheated motor or excess voltage flowing through the compressor.


Compressors typically contain a run capacitor, or device that alters current to one or multiple motor coils. If the run capacitor fails, the motor draws excess current while attempting to start, which trips or overloads its overload relay, the device that protects the motor from high voltage. This high level of voltage stops the motor from working while refrigerant continues to move through the A/C compressor, flooding it. If the system is charged with an improper level of refrigerant, caused by the technician improperly measuring the appropriate electrical charge, too much refrigerant can also flow through the compressor, resulting in flooding.


A/C compressor slugging can be prevented by ensuring the proper refrigerant charge calculations. Opening the compressor and inspecting for faulty components, such as a failed run capacitor, and replacing them as necessary can help prevent slugging.

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