Armstrong Air
Blower Stuck in Fan-On Mode
Furnace blower runs continuously even when there is no call for heat or cool.
Advertisements
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.
Advertisements
Possible Causes
Thermostat fan set to ON instead of AUTO, Stuck blower relay on control board, High limit switch open, Shorted G (fan) circuit
How to Fix / Troubleshooting
Steps to check:
- Thermostat setting: Verify the thermostat fan mode is set to AUTO, not ON.
- Check LED code: Look at the Armstrong Air control board. If a high limit fault is present, the board may run the blower continuously for safety. Address overheating causes (filter, ducts).
- Inspect G circuit: Turn off power and disconnect the G wire at the furnace control board. Restore power. If the blower stops, the thermostat or wiring is calling for fan. If it continues, the blower relay on the board may be stuck.
- Replace control board: If the blower relay is welded closed, the integrated furnace control board must be replaced.
Advertisements
Repair Difficulty
Medium
3/5
Required Part
Integrated Furnace Control Board
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements