CTC Blower Stuck in Continuous Mode

Furnace blower runs continuously even when there is no call 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, High limit switch open, Miswired thermostat

How to Fix / Troubleshooting

Safety first: Turn off power before accessing the control board.

Steps:

  • Check the thermostat fan setting and ensure it is set to AUTO, not ON.
  • If the blower continues to run, remove the blower door and inspect the CTC control board. Some models have a manual fan ON jumper; verify correct configuration.
  • Check if the high limit switch is open (furnace may run blower to cool down). Correct airflow issues and reset/replace the limit if needed.
  • If the blower relay on the board is welded closed (you may hear a constant click or see burn marks), the control board will need replacement.
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Repair Difficulty

Medium 3/5

Required Part

CTC Integrated Furnace Control Board
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