Field pattern: electric water heater 'fixed' by pressing reset, cold again days later (find what tripped the ECO)
The reset button is a high-limit (ECO) safety that opens when the water overheats. It does not fail by itself very often; something drove the water too hot: a thermostat stuck closed, an element shorted to the tank, or a loose, overheated wire. The wrong turn is pressing reset and leaving, or replacing only the upper thermostat without testing the elements and the wiring.
Cross-checked ~60 min moderateBrands: All
Before you start
- Turn off the breaker and verify zero voltage at the upper thermostat terminals before touching anything; the heater runs on 240 V
- Live-voltage tests only with insulated probes, one hand, dry floor; replace insulation and covers before restoring power
- Never run an element dry; the tank must be full before power is restored
- Manufacturers state the cause of a tripped high limit must be found before the heater goes back in service
Diagnostic steps
Unlock all 7 steps with expected values
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