Hermetic refrigerator compressor, the black sealed unit at the back bottom of a fridge

How to test a refrigerator compressor start relay (PTC) and overload (electrical only)

The start device (PTC or current relay) and the overload plug onto the compressor terminals. Test them off the compressor. Electrical tests only: any compressor replacement, refrigerant work or brazing is a sealed-system job for an EPA 608-certified technician.

Cross-checked ~30 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
Pull the relay straight off the pins; do not pry or bend the compressor terminals
A hissing or oily compressor terminal means refrigerant leak risk: stop, ventilate, and refer to an EPA 608-certified technician
Sealed-system work (compressor change, recharge, brazing, leak repair) is blocked: refer only

Diagnostic steps

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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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