US Stove
Thermostat Control Failure
Furnace runs continuously and overheats the house; does not shut off when thermostat is satisfied.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Thermostat contacts stuck closed, Shorted thermostat wiring, Incorrect thermostat mode, Control board relay stuck
How to Fix / Troubleshooting
Safety first: If the furnace will not shut off, turn off the main power switch or unplug the unit.
Steps:
- 1. Check thermostat settings: Ensure the thermostat is set to the correct mode and temperature. Turn it down below room temperature to see if the furnace should stop.
- 2. Inspect thermostat wiring: At the furnace, disconnect the thermostat wires from the control board. If the furnace stops calling for heat, the thermostat or wiring is likely at fault.
- 3. Test thermostat: Replace the thermostat with a known-good compatible unit or temporarily operate the furnace in manual mode if supported.
- 4. Control board relay: If the furnace continues to run even with thermostat wires removed, the control board’s call-for-heat relay may be stuck closed. Replace the control board.
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Repair Difficulty
Medium
3/5
Required Part
Thermostat or Main Control Board
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