How to check a defrost timer in a refrigerator?

Directions for testing a refrigerator defrost timer.

Before you begin to test your defrost timer, make sure you disconnect the appliance's power supply. The easiest way to do this is to unplug the unit from the wall. Alternatively, you could trip the appropriate switch in the circuit breaker panel, or you could remove the appropriate fuse from your home's fuse box.

Consult with an appliance repair technician if you do not feel you have the skill or the ability to successfully complete this repair.

  1. Locate your defrost timer. It can be located behind the refrigerator's lower kickplate, in the refrigerator's control panel, or even behind the refrigerator on its back wall. Defrost timers almost always have four metallic terminals extending from the bottom. Once you have found your refrigerator's defrost timer, remove it for testing.

  2. Remove all the screws holding the timer and pull the timer carefully out of the refrigerator. Pull it out far enough so that you can disconnect its wires.Be sure to label the wires and note their location. Pull firmly on the wire's connectors to remove them. You may need to rock them back and forth a little to ease the motion.

  3. Use a multimeter to test the timer for continuity. Set your multimeter to the R X 1 scale. Place one of the meter's leads on the common terminal. It should be labeled "3" or "C". If none of the terminals are labeled, you can locate the common terminal by determining which terminal coincides with the white wire in the connector plug. With one multimeter lead (probe) touching the common terminal, touch the other lead to the other three remaining terminals, one at a time. Testing the first pair should produce a reading of zero, or near zero, denoting continuity. The second pair may also result in a reading of zero or near zero. Testing the third pair of terminals should produce a reading of infinity.

  4. Find your refrigerator's timer switch and turn it in a clockwise motion until it clicks. Use your multimeter and test the terminals again in the same manner as in the preceding paragraph. In this test, one of the pairs of terminals should produce a reading of continuity. At least one pair, but maybe two, should produce a reading of infinity. One important note to keep in mind is that a pair of terminals that demonstrated continuity in the first test should now demonstrate infinity. Likewise, a pair of terminals that demonstrated infinity in the first test should now demonstrate continuity.

  5. If the test you conduct with your defrost timer does not produce these results, then you should replace the timer.


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