The furnace runs but produces no heat; the blower runs continuously, circulating room temperature air.

Critical safety: If you smell gas, shut off the gas supply, evacuate, and contact your gas utility.

• Thermostat check: Ensure the thermostat is set to HEAT and the temperature is above room level.
• Verify gas valve position: Locate the manual gas shutoff near the furnace and ensure it is parallel to the pipe (open position).
• Observe ignition: Through the sight glass, watch for ignitor glow and burner flame when there is a call for heat. No glow suggests ignitor failure; a glow with no flame suggests a gas supply or valve issue.
• Inspect ignitor: With power OFF, inspect the ignitor for cracks or damage, and replace it if necessary.

If the ignitor works but burners never light, gas pressure and valve operation must be checked by a licensed technician.