How to troubleshoot a Whirlpool refrigerator that keeps icing up the coil in the freezer

Ron wrote:

Hi. I have a 20-year old Whirlpool Fridge; top freezer model # ET18ZKXXW00. I love the fridge, but…about 6 months ago i replaced the defrost timer on the advice of an appliance parts store. Fridge was always running, freezer was full of ice and fridge unit was warm.

i took the back off and it too was covered in ice. I defrosted everything, replaced the timer and the unit is still constantly running.

Last week i unplugged it for a couple of hours to melt some of the ice in the freezer, took the back off and melted the ice that was encasing the coils.

what could the issue be?

Two problems right off the bat:

1. You replaced the defrost timer without knowing or proving that it was the real problem or bad to begin with.

2. You didn’t buy your parts thru! 🙁 Fun fact to know and tell: if you had purchased the defrost timer thru this site and it didn’t fix the problem, you could have returned it for a refund! Can you do that at your parts store? No? So… Why do you buy there?

Okay, enough scolding. Let’s get your fridge fixed!

The defrost system consists of three components: the defrost timer, the defrost thermostat, and the defrost heater. If any one of these three components goes bad, then the refrigerator will not defrost and ice will accumulate on the evaporator coil as you are seeing. Since you have already replaced the defrost timer, that only leaves the other two components as possible suspects.

Both the defrost heater and the defrost thermostat are easy to test with a multimeter. For the defrost heater, measure the resistance through the heater with your meter. The resistance should be something in the low ohms; the exact ohm reading is not important as long as it is something low. High resistance in the kilo-ohms or mega-ohms range or open is a bad defrost heater and it should be replaced.

To test the defrost thermostat, remove the thermostat from the evaporator by unclipping it and place it into a glass of ice water. Let the defrost thermostat sit in the ice water for about five or ten minutes and then measure the continuity through the defrost thermostat. Again, if it reads open or very high resistance, then the defrost thermostat is bad and must be replaced.

Not surprisingly, you can buy the new defrost heater or new defrost thermostat right here through this website! 8) Just enter your model number here ==>

If you need more help troubleshooting and repairing your refrigerator, come start a new topic in the Kitchen Forum at the Appliantology Academy and we’ll step you thru it for free ==>


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