Furnace will not start; status LED flashes 1 time repeatedly on the Miller control board.

Safety first: Turn off electrical power to the furnace at the service switch or breaker and shut off the gas valve before touching any internal components. If you ever smell strong gas, evacuate and contact the gas utility or fire department.

This code usually indicates the furnace tried to light but did not detect flame.

• Check gas supply: Verify the manual gas shutoff valve near the Miller furnace is fully open. Confirm other gas appliances in the home work.
• Inspect the hot surface ignitor: Remove the burner access panel. Locate the ignitor (usually mounted at the burner assembly). Look for cracks or white spots on the element. If damaged or not glowing during a call for heat, replace the ignitor with the correct Miller OEM hot surface ignitor.
• Clean the flame sensor: Locate the flame sensor rod near the burner. Remove the mounting screw, pull the rod out, and gently clean it with fine steel wool or a Scotch-Brite pad until shiny. Reinstall and ensure the wire connection is tight.
• Check wiring: Inspect the harness from the ignition control board to the ignitor and flame sensor for loose plugs or burned wires. Reseat connectors firmly.
• Reset lockout: Restore power, set thermostat to call for heat, and observe the ignition sequence. If the furnace still fails to light after several tries, the ignition control board or gas valve may be faulty and should be tested by a qualified technician.