Concord Blower Stuck On

Furnace 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

Thermostat fan set to ON, Stuck blower relay on control board, Open limit switch, Shorted thermostat wiring between G and R

How to Fix / Troubleshooting

Safety: Turn off power before working on wiring or control board.

Steps:

  • Check thermostat: Ensure the fan setting is on AUTO, not ON. If set correctly and blower still runs, proceed.
  • Inspect limit switch: If the high limit is open, many Concord furnaces will run the blower continuously. Check for LED codes indicating a limit fault and address overheating causes (filter, airflow).
  • Check thermostat wiring: At the furnace control board, remove the G wire from the G terminal. If the blower stops, the issue is in the thermostat or wiring. If it continues, the blower relay on the board may be stuck.
  • Control board: If the blower relay is welded closed, the integrated furnace control board will need replacement.
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Repair Difficulty

Medium 3/5

Required Part

Integrated Furnace Control Board
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