Furnace Won’t Turn On? What to Check First
It’s always the first cold night. Here’s what to check before you call, straight from the no-heat calls we run every winter around Sandy and the Salt Lake Valley.
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Common Furnace Problems
Most no-heat calls in the first cold snap are something small. Try these first.
Why won’t my furnace turn on?
Start with the thermostat. Make sure it’s set to heat, the temperature is set above the room, and the batteries aren’t dead. Then check that the furnace switch is on (it looks like a light switch near the furnace) and that the breaker isn’t tripped. If all that’s fine, the usual culprits are a dirty flame sensor, a safety switch that tripped, or a clogged filter.
Why is my furnace blowing cold air?
Most often the furnace tried to light, failed, and is now just running the fan. A dirty flame sensor, a plugged filter, or a blocked intake or exhaust pipe will all do it. Turn the thermostat fan setting to auto instead of on, change the filter, and if it’s still blowing cold, call us.
My furnace turns on and shuts off over and over. What’s wrong?
That’s called short cycling. A clogged filter, a dirty flame sensor, or a furnace that’s overheating from poor airflow are the common causes. Overheating is a safety issue, so don’t ignore it. Check the filter first, then get it looked at.
How Long Should a Furnace Last?
And when it’s worth fixing versus replacing.
How long does a furnace last in Utah?
Most furnaces last about 15 to 20 years. Under about 10 years, parts are usually still under warranty and a repair makes sense. Past that, parts get expensive and replacing is often the better money, unless it’s been well maintained.
Is it worth getting a furnace tune-up?
Yes, especially before winter. A $69 tune-up checks the flame sensor, safeties, electrical, and airflow, and catches the stuff that causes most no-heat calls, like a dirty flame sensor or a clogged secondary heat exchanger. It’s a lot cheaper than a 2am emergency call.
When to Call Instead of DIY
The simple checks are worth trying. Past that, here’s when to pick up the phone.
- You smell gas (leave first, then call the gas company)
- The furnace is banging, squealing, or smells like burning
- It keeps shutting off on its own
- The same problem keeps coming back
- You tried the simple stuff and it’s still not working
Still No Heat? We Can Help.
We answer 24/7 and get out same day whenever we can. Weekday service calls are $39 and go toward the repair. After hours, weekends and holidays are $99. You get the price in writing before we start.
More help: Furnace Repair · Emergency Furnace Repair · Furnace Tune-Up · Furnace Replacement