Troubleshooting Fridge Won`t Defrost

Refrigerator is Not Defrostin

How do I Fix my Refrigerator?

When the ice builds up on the inside of your freezer or there are uneven temperatures, it is possible that the fridge defroster in the freezer or refrigerator is not working. An imbalance in the fridge’s temperature is caused by the malfunctioning refrigerator defroster. This can be caused by many things, including the defrost control board, the defrost timer, the defrost heater assembly, the defrost thermostat, defrost sensor’s fuse, or the main control board. What follows is a troubleshooting list for each of these parts.

What to Check:

Defrost Control Board

If your freezer has uneven temperatures between the front and back, or top and bottom, you will need to check the defrost control board. To check the defrost control board, first unplug the fridge and move it out from the wall. The defrost control board is located at the back of the refrigerator. It can be tested for effectiveness using an ohmmeter, which measures electrical resistance on a circuit.

Defrost Control Board

Defrost Heater Assembly

When this is broken, the defrost cycles of the fridge is ceased and unbalanced. There may cause unusual much of the frost on the walls of the freezer. First, unplug the refrigerator and disconnect any wires from the defrost heater. The defrost heater is behind the back access panel inside the fridge/freezer, under the evaporator coil. Second, take a digital multimeter, or DMM, and use it to test the ohms. Place the probes on the heater’s terminals, one for each. The good number is between 10 – 150 ohms. If you have a thermostat, make sure it is cooled off before doing the test.

Defrost Heater Assembly

Defrost Timer

This is a little part with a big job: to keep the fridge’s system cycling between heating and cooling in order to maintain appropriate temperatures. It is located in one of these common locations: behind the front grill, inside the fridge or freezer, in the temperature console, or behind the fridge, near it’s compressor. If you suspect it is not working, you might want to put it in defrost, wait half an hour and see if the heater comes on. To check the timer, first, undo the screws holding it in place. Second, disconnect and unplug it. Third, use a DMM to test the timer for continuity.

Defrost Timer

Defrost Sensor with Fuse

If your refrigerator is too either warm or cold, it could be because the defrost sensor’s fuse has blown. This is another failsafe. If the defrost sensor does not register that the system is getting too warm, the heater won’t shut off. To prevent the extra heat from becoming a problem, the sensor has a fuse that blows. When the fuse blows, it shuts off the power to the defrost heater. The defrost sensor only has one fuse. If this fuse blows, the defrost sensor is broken and must be replaced. Both the sensor and the fuse may be tested with a DMM.

Defrost Sensor with Fuse

Defrost Thermostat

The defrost thermostat is responsible for sending a signal to the defrost heater assembly so that it knows when to turn on. When the thermostat breaks down, the heater no longer gets the message to defrost the evaporator coils, giving us yet another reason that a fridge or freezer may not be defrosting. It can be tested through the use of a DMM. First adjust the thermostat to the lowest temperature possible, then check its continuity with the DMM.

Defrost Thermostat

Main Control Board

The defrost system is controlled by a main control board. The main control board also maintains the flow of power to other parts of the fridge. If the board isn’t working, it could affect any one of the fridge’s systems, including the defrost system. However, it is important to check all of the components of the defrost system in order to prove your hypothesis before replacing such a major part.

Main Control Board
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