How to Fix / Troubleshooting

Safety first: Turn off power and gas. Wait for moving parts to stop before touching the fan.

Inspect fan wheel: Remove the combustion chamber cover and visually inspect the flue fan wheel for debris or damage. Clean gently with a soft brush.
Check electrical connections: Locate the multi‑pin connector from the fan to the Sime control board. Ensure it is fully seated and free of corrosion or heat damage.
Spin test: With power off, rotate the fan wheel by hand. It should spin freely without grinding. If stiff or noisy, the fan bearings may be failing and the fan assembly should be replaced.
Reset and test: Restore power and call for heat. If the error reappears and the fan does not reach commanded speed, a new fan or control board may be required. This should be confirmed by a technician with proper diagnostic tools.

Furnace displays a fan speed or fan tachometer error; burner does not ignite.

Possible Causes