BLOWER FLASH ONLY (NO HEAT)
York
Stuck Fan Relay / Fan On with No Heat
Indoor blower runs continuously, no heat; York board LED indicates continuous fan mode or fan-only fault (no numeric code).
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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, Shorted G (fan) thermostat wire to R, Faulty thermostat
How to Fix / Troubleshooting
Safety: Turn off power before accessing control wiring.
- Check thermostat: Ensure the fan setting is on AUTO, not ON. Set system to HEAT and raise temperature to call for heat.
- Inspect thermostat wiring: Remove the furnace blower door and locate the low-voltage terminal strip (R, W, G, Y, C). Look for the green G wire touching R or other terminals. Correct any shorts.
- Test G circuit: With power off, temporarily remove the G wire from the board. Restore power. If the blower stops running constantly, the issue is in the thermostat or wiring. If it still runs, the board relay may be stuck.
- Replace thermostat or board: If wiring is good and the thermostat is suspect, replace it with a compatible model. If the board relay is stuck closed, the integrated control board will need replacement by a technician.
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Repair Difficulty
Medium
3/5
Required Part
Integrated Furnace Control Board
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