Identifying a thermal fuse (TCO) or snap-disc thermostat by its markings when you need a replacement
Thermal fuses (thermal cutoffs, TCOs) are one-shot: they open permanently at their rated functioning temperature. Snap-disc thermostats and limits are reusable bimetal switches that open (or close) at a set temperature and either reset automatically when they cool or need a manual reset button. To replace either one you must match: temperature rating, switch action (normally closed vs normally open, opens on rise), reset type, electrical rating (amps and volts, AC vs DC), and physical form (axial leads, terminals, mounting style, surface vs air-stream). The OEM part for the appliance model is always the first choice; universal parts are a fallback, never a guess.
Before you start
- A blown thermal fuse or tripped limit is a symptom: find and fix the overheating cause (blocked vent, failed fan, stuck relay) first; see component-thermal-cutouts
- Never bypass or jumper a thermal fuse or limit to 'test run' an appliance and leave it
- Never install a part with a higher temperature rating than the original
Diagnostic steps
Unlock all 6 steps with expected values
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