Furnace cycles on and off or will not start; Miller LED flashes 8 times repeatedly.

Safety: Turn off power and gas before servicing. Repeated ignition failures can allow unburned gas to accumulate.

• Reset lockout: Turn furnace power off for at least 30 seconds, then back on. Call for heat and observe the full ignition sequence.
• Check ignitor glow: The hot surface ignitor should glow bright orange. If it is dim or slow to heat, replace it with the correct Miller OEM ignitor.
• Inspect gas valve operation: Listen for the gas valve click after the ignitor heats. If there is no click, test for 24V at the gas valve terminals during ignition. If voltage is present but no gas flow, replace the gas valve. If no voltage, suspect the control board.
• Verify burner alignment: Ensure the ignitor is properly positioned in the gas stream and near the burner ports. Misalignment can prevent reliable lighting.
• Replace control board if needed: If all components test good but lockouts continue, the Miller ignition control board may be failing and should be replaced.