Whirlpool Refrigerator Bimetal Defrost Thermostat Parts — Models & Compatibility

If your Whirlpool, Kenmore, KitchenAid, or Maytag refrigerator won't stop running or you're dealing with frost buildup in the freezer, the bimetal defrost thermostat is likely the culprit. This small component regulates the defrost cycle timing — when it fails, your fridge either runs continuously trying to maintain temperature or doesn't defrost properly. The 4387503 thermostat (also sold as WP4387503) fits over 100 refrigerator models across multiple brands in the Whirlpool family.

Is This the Right Part for Your Model?

Check your refrigerator's model number before ordering. You'll find it on a metal tag inside the fresh food compartment — usually on the left or right wall, near the top. It starts with letters followed by numbers, like ET18NKXAW02 or 3VET19ZKBW00. Cross-reference your full model number with the compatibility list below to confirm this thermostat fits your specific unit.

About This Replacement Part

The bimetal defrost thermostat is a temperature-sensitive switch mounted on the evaporator coils in your freezer section. It works with the defrost timer and heater to prevent ice buildup. When the coils reach a certain temperature during the defrost cycle, the bimetal disc inside the thermostat flexes and breaks the circuit, stopping the heater. If this thermostat sticks open, your defrost heater won't activate and ice accumulates. If it sticks closed, the heater runs too long and you'll notice warmer temps or water pooling in the bottom of your freezer. This is a direct OEM-quality replacement that restores proper defrost cycling without the dealer markup.

Compatible Whirlpool Refrigerator Models

This defrost thermostat works with the following refrigerator model numbers. If you don't see your exact model listed, check the product page for the complete compatibility database:

• ET Series: ET18NKXAW02, ET20DKXAB01, ET22DMXDN00, ET20NKXAW04, ET22DKXAN04, ET25DKXDW00, ET20HDXBW00, ET25DQRBW01
• 3ET/3VET Series: 3ET18DKXAW00, 3ET22DKXBW00, 3VET19ZKBW00, 3VET21DKBW00
• 4ET Series: 4ET18ZKXBN00, 4ET20ZKXBN00

This part replaces manufacturer numbers 2149641, 4343917, 61002113, and AP6009317. It's compatible with Whirlpool, Kenmore, KitchenAid, and Maytag top-mount and side-by-side refrigerators manufactured between the late 1990s and mid-2010s.

Installation Considerations

Replacing the defrost thermostat requires accessing the evaporator cover inside your freezer compartment. You'll need to remove frozen food, take out freezer shelves, and unscrew the back panel. The thermostat clips onto the evaporator coils with a spring clip and connects via two wire terminals. Most DIYers complete this repair in 30-45 minutes. Make sure to unplug the refrigerator before starting any repair work, and let the evaporator coils thaw completely if there's heavy ice buildup — otherwise you won't be able to access the mounting location properly.

Why This Part Fails

Defrost thermostats typically fail after years of thermal cycling. The bimetal disc fatigues from repeated heating and cooling, eventually losing its spring tension or cracking. Moisture intrusion can also corrode the contacts, preventing proper circuit operation. High-use households and humid environments accelerate wear. If your refrigerator is 8-12 years old and you're experiencing defrost issues for the first time, the thermostat has likely reached end-of-life and needs replacement rather than troubleshooting.