08
American Standard
Stuck Fan Relay or Fan On After Power Up
Error code 08 and indoor blower runs continuously, no heat call recognized
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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
Failed blower relay on integrated furnace control, Miswired G (fan) thermostat circuit, Short between R and G thermostat wires, Faulty thermostat stuck in fan ON mode
How to Fix / Troubleshooting
Safety: Turn off power before removing the blower door or touching wiring.
Error 08 indicates the control detects a fan relay problem or continuous fan call.
- Check thermostat settings:
- Ensure the fan setting is on AUTO, not ON.
- Turn system to OFF and see if the blower stops after a few minutes.
- Inspect thermostat wiring:
- At the furnace control board, verify that the G wire is connected only to the G terminal and not shorted to R.
- Look for crushed or pinched thermostat cable along its run.
- Test the board fan relay:
- With power off, disconnect the G wire from the board.
- Restore power; if the blower still runs with no G call, the fan relay on the board is likely stuck closed.
- Replace the integrated furnace control with the correct American Standard part number.
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Repair Difficulty
Hard
4/5
Required Part
Integrated Furnace Control Board
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