Why Won’t My Furnace Turn On?
A furnace that does not start may have a thermostat, power, ignition, condensate, or safety-control issue. Check the safe basics, note any indicator code, and avoid repeated resets.
Read the guide →Common causes
Thermostat set to Fan instead of Auto, a clogged filter restricting airflow, an ignition fault, or a safety control shutting the burner down while the blower keeps running.
What to check safely
Thermostat mode and temperature, filter condition, and whether vents are blocked. Do not open gas components or bypass safety switches.
When to call
If cold air continues after the safe checks, or if the furnace cycles on and off without heating, arrange diagnosis. The cause depends on the equipment and needs testing.
Key takeaways
- Check thermostat mode (Auto, not Fan), filter condition, and blocked vents.
- Cold air with the blower running often means the burner is shutting down on a safety control.
- If cold air continues after the safe checks, arrange diagnosis — the cause needs testing.
