Common furnace problems
No heat at all
Check the thermostat mode and batteries, the breaker, and the furnace power switch (it looks like a light switch near the unit).
Short cycling
A dirty filter or flame sensor is common. So is an overheating heat exchanger.
Burning smell
A light dust smell on the first cold day is normal. A strong or lasting smell is not: shut it off and call.
Blower runs, no heat
Could be ignition, gas valve or flame-sensing trouble.
What to tell the technician
- The furnace's age and whether it's gas or electric (or a heat pump).
- Any blinking light codes on the control board (visible through the panel window).
- When the problem started and whether it's constant or occasional.
FAQ
Why does my furnace turn on then shut off?
Common causes include a dirty flame sensor, a clogged filter causing overheating, or a venting or pressure switch problem. A technician can test each.
What should I do if I smell gas?
Leave the house, don't operate switches, and call your gas utility or 911 from outside. Don't call a contractor first.
Do I need a carbon monoxide alarm?
California law requires carbon monoxide alarms in homes with a fossil-fuel appliance or an attached garage. Test them regularly.