Tempstar
Stuck Blower Relay or Open Limit Switch
Blower runs continuously even when thermostat is not calling for heat or fan.
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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
Fan set to ON at thermostat, Stuck blower relay on Tempstar control board, Open high limit switch, Short between G and R thermostat wires
How to Fix / Troubleshooting
Safety: Turn off power before accessing the control board.
- Step 1 – Check thermostat fan setting: Ensure the thermostat fan mode is set to AUTO, not ON.
- Step 2 – Disconnect thermostat: Remove the thermostat from its base or disconnect thermostat wires at the furnace. If the blower stops, the issue is in the thermostat or wiring.
- Step 3 – Inspect G wire: Look for shorts between the G and R wires in the thermostat cable. Repair or replace damaged cable.
- Step 4 – Test limit switch: If the blower continues to run with thermostat disconnected, test the high limit switch for continuity. An open limit can cause continuous blower operation.
- Step 5 – Check blower relay: If the limit is closed, the blower relay on the Tempstar control board may be stuck. Replace the control board if the relay is welded closed.
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Repair Difficulty
Medium
3/5
Required Part
Tempstar Integrated Furnace Control Board
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