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How to test a refrigerator defrost thermostat



Common refrigerator defrost thermostat Directions for testing a refrigerator defrost thermostat.

Before you begin to test your defrost thermostat, 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 refrigerator's defrost thermostat. In freezer-on-top models, it may be located under the floor of the unit, or it could be found at the back of the freezer. If you have a side-by-side refrigerator, the defrost thermostat is found at the back of the freezer side. The thermostat is wired in series with the defrost heater, and when the thermostat opens, the heater shuts off. You will have to remove any objects that are in your way such as the contents of the freezer, freezer shelves, icemaker parts, and the inside rear, back, or bottom panel.


  2. The panel you need to remove may be held in place with either retainer clips or screws. Remove the screws or use a screwdriver to release the clips holding the panel in place. Some older refrigerators may require that you remove a plastic molding before you can gain access to the freezer floor. Exercise caution when removing the molding, as it does break fairly easily. You could try warming it with a warm, wet towel first.


  3. There are two wires leading from the thermostat. They are attached to terminals with slip-on connectors. Gently pull on the connectors to release the wires from the terminals. You may need to use needle nosed pliers to help you. Do not pull on the wires themselves.


  4. Proceed to remove the thermostat. It may be secured in place with a screw, clip, or clamp. The thermostat and the clamp on some models are one assembly. On other models, the thermostat clamps around the evaporator tubing. In some other cases, the thermostat is removed by squeezing in on the clip and pulling the thermostat up.


  5. Set your multitester to the R X 1 ohms setting. Place each of the multitester's leads on a thermostat wire. When your thermostat is cold, it should produce a reading of zero on your multitester. If it is warm (anywhere from forty to ninety degrees Fahrenheit), then this test should produce a reading of infinity. If the results you receive from your test differ from the ones presented here, then you will need to replace your defrost thermostat.