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Customer Questions and Answers for Defrost Bimetal by Whirlpool

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Manufacturer Part
4.89 (64)
By: Whirlpool
Part Number: OEM18027960
Manufacturer Part Number: WP4387503

The Defrost Bimetal is an OEM part for Whirlpool refrigerators. It acts as a safety thermostat that monitors and controls the temperature during the defrost cycle. This component ensures that the defrost heater turns off when the evaporator coil reaches a specific temperature, preventing overheating and potential damage.

Causes of failure may include a malfunction due to wear and tear over time, electrical failure, or damage from moisture and ice.  

Symptoms of a bad Defrost Bimetal include:

  • The refrigerator is constantly running without cycling off
  • Frost buildup on the evaporator coils, leading to reduced cooling efficiency
  • The refrigerator or freezer compartment is too warm
  • Unusual fluctuations in refrigerator temperature

This OEM Whirlpool part is also compatible with Maytag, KitchenAid, Jenn-Air, Amana, Magic Chef, Admiral, Norge, Roper and some Kenmore models.

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Questions & Answers

For Whirlpool Defrost Bimetal (Part Number: OEM18027960)

Jim for Model Number GR9FHKXPB00

I replaced my defrost timer a few weeks ago, as the original timer was sticking in defrost mode. I confirmed that the timer was hooked up correctly as there is an extra black wire which I installed on terminal #1. The new timer worked great for 5 or 6 days, and then stuck again in defrost mode. When I advance the timer manually with a screwdriver, it works okay for a few days, then sticks again in defrost mode. Do you think I might have gotten a defective timer as a replacement , and buy another one? I'm thinking the defrost bi-metal (part# 4387503) might be causing the problem. Your help in this matter is greatly appreciated.

1 Answer

Hello Jim. Black wire is in wrong location on the timer. For cumulative run timer push slotted loose timer motor lead over & all the way down terminal number 2 with wire toward timer motor.

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1 Answer

Hello Bert. The wire colors do not matter. The Bi-metal WP4387503 is a closed circuit. As long as the temperature when it opens is the same, that is all that matters.

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1 Answer

Hello Jim, I would check the start relay on the compressor to see if it is bad. Normally when you pull the relay off and shake it against your hand, there might be particles of ceramic that come out. If this happens then you would need a new relay. We would need to verify your refrigerator model number to help further. Please post your model number with a new question on the parts page. http://www.appliancepartspros.com/modelnumber_locator.aspx

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1 Answer

Hello John. It sounds like you may have a defrost problem with the unit. Check and see if there is any frost build up on the back wall of the freezer. If so, you will need to test the defrost heater and the defrost thermostat. They should read closed for continuity when cold. You can test this with a multi-meter TJMA-DMT3. I will include a link at the end to assist you how to use the multi-meter if needed. If both parts are good, you will need to replace the defrost timer. Once the problem is repaired, you will need to thaw out the ice on the coils before the unit will operate properly. http://forum.appliancepartspros.com/oven-repair-including-ranges-cooktops/4810-how-check-continuity-ohmmeter.html

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Michael for Model Number ET8LFKXKQ01

I am considering the bi-metal defrost thermostat being the problem. The coil in the back wall of the freezer compartment totally ices up. The icemaker production slows down and both the refrigerator and the freezer are not as cool as normal. After turning the unit off and defrosting everything, including the ventilation tube the scenario repeated itself after a few days. I can advance the defrost timer manually and the unit shuts off. During this period I can detect no noise indicating a thawing process, and it seems the only time the unit shuts off automatically is when the temperature dial is raised to the warmest position.

1 Answer

Hello Michael, I'm assuming that when you force the unit into defrost at the defrost timer it is cycling itself back out of defrost by itself. If not, the defrost timer isn't advancing and will require replacement. If it is then the defrost thermostat or the heater are the main concerns. The thermostat cannot be tested unless it's below about 25°F. In this state it will be closed, (zero resistance). Also, this defrost thermostat WP4387503 has the epoxy top so you should examine it carefully as if the epoxy is protruding from the metal cup, it has been contaminated with moisture and requires replacement. Let me know if I can assist you futher.

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1 Answer

Hello Steve. Sounds like your defrost drain has frozen up. This isn't a big deal, just time consuming. You have to remove the back wall of the freezer compartment and get you hair dryer. The defrost drain is in the floor in the back of the freezer compartment (usually in the center). I usually use a paint scraper to remove all of the ice I can get out without damaging any Styrofoam. Then use the hair dryer to start melting ice. When the ice is gone except for the ice in the drain hole, I use a screwdriver to transfer the heat,(I stand the screwdriver up on the ice in the hole and heat the screwdriver shaft with the hairdryer). This method works great but is, as I said, a time consuming endeavor. You can speed things up if you have a portable steamer used for steaming clothes. It will melt the ice faster but you have to also use a shop vac to catch all of the water it produces. Once you get the drain clear, use a piece of weed eater string to chase the entire drain (never use wire or anything that can puncture the rubber drain tube!). After this is complete, I always put about a tablespoon of white vinegar in the drain to prevent algae formation which will also cause the drain to stop up again. Next, set the freezer to one number warmer, which will prevent the drain from freezing again if it froze due to excessively low temperatures. Good luck and I sure hope I've helped!

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1 Answer

Hello Jose. Check and see if the compressor is running. If not, test for power to the compressor. If there is none there, and the defrost board is new, you may have a broken or bad wire on the unit. You will need to track the wires and check the connectors. You can test this with a multi-meter TJMA-DMT3. Here is a link on how to use a multi-meter. Hope this helps. http://forum.appliancepartspros.com/oven-repair-including-ranges-cooktops/4810-how-check-continuity-ohmmeter.html

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1 Answer

Hello Jose. It sounds like you may have an issue with the defrost board 12050506. This powers the evaporator fan motor and works with the cooling of the unit. This part has been permanently discontinued by the manufacturer and we don't know of any source or replacement for the part. Thanks.

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1 Answer

Chris, A visual inspection won't work, You will need to test the defrost thermostat WP4387503 and heater WP2315530 for an "open"(no resistance) circuit or a "closed"(continuity) circuit with a multimeter. To access the heater and thermostat, you will need to remove the back wall of the freezer compartment, carefully disconnect the wire harnesses, and of course, you need to unplug the power cord first. The defrost thermostat has to be in an ice water bath in order for it to be a closed circuit. If the components test proper with a meter, you pretty much have it isolated to a bad defrost control/timer W10822278 located in the control panel assembly in the ceiling of the fridge compartment. Thanks and Good Luck

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