How to troubleshoot a freezer compressor

Written by martha richardson
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A compressor, one of the four essential components needed to produce refrigeration in the freezer, is an electromechanical device that employs an electric motor to drive a mechanical pump. When the compressor malfunctions, it can be due to a mechanical or electrical problem. The motor might be working but the compressor might fail to pump because of defective valves, or the valves might be good but the motor might fail to run because of defective windings. If the windings are shorted or open, the compressor will not work

Skill level:

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Things you need

  • Flat-blade screwdriver
  • Phillips screwdriver
  • Multimeter
  • Electrical tape
  • Flashlight

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  1. 1

    Put a pocket thermometer inside the freezer compartment to see if it will cool. You should see a drop in temperature within 15 to 20 minutes. While waiting, feel the inside of the freezer with your hand to get an indication of any cooling.

  2. 2

    Use a flashlight to locate the compressor at the back of the freezer. While it is running, feel the two lines coming from the compressor. The discharge line should be warm to touch, and the suction line should be cold.

  3. 3

    Check the wall outlet for power using a multimeter if the freezer compressor fails to run. Once power is established, unplug the unit and locate the electrical connection to the compressor. Remove the cover, then remove the relay and overload. The relay has a coil with two push-on electrical connections. The overload is a circular disk with two electrical connections.

  4. 4

    Set the multimeter to ohms on the scale RX1. Check the overload for continuity.

    If reading is zero ohms, overload is good. If the reading is infinity, the overload is bad and must be replaced.

  5. 5

    Check the resistance between each of the three terminals protruding from the compressor. You should get 3 different readings, depending on the compressor manufacturer and horsepower : approximately 5, 10 and 15 ohms. If any of the readings are zero or infinity, the compressor is bad and must be replaced.

Tips and warnings

  • With the ohm meter on the scale RX100K, check each terminal to ground. This should read infinity. If zero, or low reading, the compressor id defective and should be replaced.
  • If the discharge line is lukewarm, the compressor valves may be defective and not pumping or the freezer may be low on gas. A qualified technician would need to handle pressure gauges to determine which.

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