Heil furnace status LED flashes 1 time repeatedly; furnace will not start heating cycle.

Safety first: Turn off power to the furnace at the service switch and shut off gas at the gas cock before removing panels. If you ever smell strong gas, evacuate and call the gas utility or a professional immediately.

Steps to check:

• Verify gas supply: Make sure the manual gas shutoff valve near the Heil furnace is parallel to the pipe (open). Confirm other gas appliances in the home work.
• Inspect the hot surface ignitor: Remove the burner compartment door. Locate the ignitor (usually mounted near the burners). Look for cracks or white spots on the silicon carbide element. If damaged or not glowing during a call for heat, it likely needs replacement.
• Check flame sensor: The flame sensor is a small metal rod in front of a burner. Remove the mounting screw and gently clean the rod with fine steel wool or emery cloth to remove oxidation. Reinstall firmly.
• Observe ignition sequence: Restore power and call for heat at the thermostat. Watch through the sight glass: inducer starts, ignitor should glow, then gas valve should click and burners light. If ignitor glows but burners never light, suspect gas valve or gas supply. If ignitor never glows, suspect ignitor or control board.
• Reset lockout: Turn power off to the furnace for 30 seconds, then back on to clear lockout and see if the furnace lights.

When to call a pro: If you confirm gas supply is present and the ignitor and flame sensor are good but the gas valve never opens, or if you are not comfortable working around gas components, contact a licensed HVAC technician.