The first cold night of the year is when furnaces that sat all summer show their problems. Some of them you can sort out in a few minutes. Here's what to check, in order.
1. The thermostat
Set it to Heat and a few degrees above the room. If the screen is blank, replace the batteries. If the fan is set to On, it blows between heating cycles, and that air feels cool: set it to Auto.
2. The power
A furnace has a switch near it that looks like a light switch, and a breaker in the panel. Make sure both are on. You can reset a tripped breaker once; if it trips again, leave it off and call.
3. The filter
A badly clogged filter can make a furnace overheat and shut itself off, then try again, over and over. Hold the filter up to a light: if you can't see through it, replace it.
4. The furnace door
Most furnaces have a safety switch that won't let them run with the front panel off or loose. Make sure it's on and seated.
5. The gas
If other gas appliances work, the gas is on. If you smell gas, don't check anything: leave the house and call the gas company or 911 from outside.
Blowing cold air?
It's normal for the first minute of a cycle while the furnace warms up. If it stays cold, the burners may not be lighting: often a dirty flame sensor or a failed igniter, both technician jobs.
When to call
- The breaker trips again after one reset
- The furnace starts, shuts off, and keeps repeating
- You hear banging, squealing or grinding
- A carbon monoxide alarm sounds: get everyone out and call 911
Please don't take the burner compartment apart. Call us at 805-965-6326; after-hours emergency service is available by phone.
Related
More tips on heating.