Load will not turn off: shorted triac or welded relay (board vs load)

When a load runs with no command, the board output that feeds it is usually shorted: triacs most often fail shorted and relay contacts can weld closed after inrush. Confirm the output is truly on with the load connected (not a ghost reading), then test the load itself, because a shorted or seized load is what usually kills the output.

Cross-checked ~40 min moderateBrands: All

Before you start

A stuck output can energize a load even when the appliance appears off; unplug before touching loads or wiring.
Live output measurements need insulated probes and one-hand technique.
Water valves stuck open can flood: shut off the supply valve first.

Diagnostic steps

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