Rheem
Thermostat or Control Stuck in Heat Call
Furnace runs continuously and overshoots the thermostat set temperature
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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
Stuck thermostat relay, Short between R and W, Misconfigured thermostat cycle rate, Faulty control board
How to Fix / Troubleshooting
Safety first: Turn off power before changing thermostat wiring.
- Check thermostat settings: Ensure the thermostat is set to the correct system type and cycle rate per manufacturer instructions.
- Remove thermostat: Take the thermostat off its base. If the furnace shuts off, the thermostat is likely faulty.
- Check R–W circuit: At the furnace, disconnect the W wire. If the furnace stops, there may be a short in the thermostat cable or thermostat.
- Board evaluation: If the furnace continues to run with W disconnected, the control board may be stuck in a heat call and require replacement.
Prolonged overheating can damage the heat exchanger; correct this issue promptly.
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Repair Difficulty
Medium
3/5
Required Part
Wall Thermostat
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