Safety: Turn off power and gas before servicing burners or gas components. Gas adjustments should be performed by a licensed technician.

Steps to check:

Clean burners: Remove the burner assembly following Armstrong Air service instructions. Use compressed air or a soft brush to remove rust and debris from burner ports. Do not enlarge the ports.
Check flame sensor position: Ensure the flame sensor tip is fully engulfed in the burner flame when operating. Adjust its position slightly if necessary, keeping it in the manufacturer’s intended location.
Inspect ignitor: A weak ignitor may not reliably light the gas, causing repeated retries and lockout. Check for hairline cracks or white spots. Replace if suspect.
Gas pressure check (technician): Have a professional verify inlet and manifold gas pressures with a manometer and adjust the gas valve regulator if needed.
Reset lockout: Turn off power for 30 seconds, then restore. If the 8-flash code returns, schedule professional service.

Furnace will not start; LED flashes 8 times repeatedly on Armstrong Air furnace board.

Possible Causes