Why won't my furnace turn on?
Check the thermostat setting and batteries, the furnace power switch and breaker, and the air filter first. If those are fine, common faults include a failed igniter, a dirty flame sensor or a blocked vent.
Many furnaces show a flashing light code through a small window on the panel. Note the pattern before you call. It helps the technician.
When is a furnace problem dangerous?
A gas smell, a carbon monoxide alarm, or scorch marks or soot around the furnace are danger signs. Leave the house and call your gas utility or 911 from outside.
Every home with a gas furnace should have working carbon monoxide alarms. Test them when you change your clocks.
Can no heat cause frozen pipes?
Yes. If the heat goes off in freezing weather, pipes in exterior walls, crawlspaces and attics can freeze. The American Red Cross recommends keeping the heat at no lower than 55°F if you're going away in cold weather.
Our frozen pipes guide covers what to do if your heat goes out.
Frequently asked questions
How often should a furnace be serviced?
Most manufacturers recommend a yearly check, usually in the fall before heating season.
Do you help with heat pumps?
Yes. See AC and heat pump repair.
Updated 2026-10-07