Snap-disc bimetal thermostats with spade terminals, similar to the cycling and high-limit thermostats in dryers and ovens

Generic photo: Retired electrician · CC0

How to test a refrigerator bi-metal defrost thermostat

The bi-metal (defrost termination thermostat) is wired in series with the defrost heater. It is closed only when the evaporator is cold and opens once the coil warms during defrost. Testing it at room temperature gives a false "bad" result: it must be cold.

Cross-checked ~45 min moderateBrands: All

Before you start

Unplug the appliance or turn off the breaker before opening panels or disconnecting parts
Take a photo of the wiring before removing any wire
Resistance and continuity tests are done with power OFF and the part isolated
Do not chip ice with tools near the evaporator: a punctured tube is a sealed-system repair (EPA 608 technician only)
Wipe up meltwater; keep the floor dry

Diagnostic steps

Unlock all 5 steps with expected values

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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

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