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No Heat in Winter: The 5-Minute Checklist Before You Call
Check the thermostat, the furnace power switch, the breaker, the filter, and the blower door, in that order. It takes five minutes and gets the heat back in a meaningful share of no-heat calls on the first hard-freeze morning of a St. Louis winter.
Do this first
The first minutes, in order
- Thermostat: set to HEAT, fan on AUTO, temperature a few degrees above the room. If the screen is blank, replace its batteries.
- Power switch: most furnaces have a light-switch-style shutoff on or beside the unit, it gets bumped in basements and utility closets. Make sure it's ON.
- Breaker: find the furnace breaker at the panel and reset it once if it's tripped, push the handle fully OFF, then ON.
- Filter: a packed filter can shut a furnace down on its safety limits. If it's gray and clogged, swap it and give the system a few minutes.
- Blower door: the front panel must be fully seated to close its safety switch, re-seat it until it clicks.
- Still nothing? Stop there. Repeated breaker resets and repeated attempts mask a real fault.
Safety first
- Never heat the house with a gas oven or range, that's a carbon monoxide risk, not a backup plan.
- Keep space heaters three feet from anything that burns, plugged directly into a wall outlet, and never running unattended or overnight.
- If you smell gas at any point, stop troubleshooting and follow the gas-smell steps: leave first, call from outside.
Stop troubleshooting and call when…
- Indoor temperature is falling fast during a single-digit cold snap, pipes can freeze in hours, not days.
- Anyone in the home is elderly, an infant, or medically vulnerable to cold.
- The furnace breaker trips again after one reset.
- You hear grinding, booming, or repeated clicking, or smell anything burning.
- The furnace starts, then shuts off again within a minute or two, over and over.
When you call Swiss Air
What we'll actually do
- Answer 24/7, a real person, not a callback queue.
- Diagnose the actual fault: ignition, flame sensor, limit switch, blower, control board, or gas valve.
- Give you the repair price up front before work starts, our No Price Change Guarantee means the quote is the price.
- If the furnace is at end of life, show you honest repair-versus-replace numbers and leave the decision with you.
Quick answers
Frequently asked
- Why is my furnace running but blowing cold air?
- Check the thermostat fan setting first, fan ON instead of AUTO circulates unheated air between cycles and is the most common cause. A clogged filter is next: it overheats the furnace so a safety switch cuts the burners while the fan keeps running. Beyond those two, cold air usually means an ignition, flame-sensor, or gas-supply problem that needs a technician.
- How cold can my house get before pipes freeze?
- Pipes in exterior walls, crawl spaces, and unheated basements are at risk once those spaces approach freezing, which can happen within hours in a Missouri cold snap even while the living space still reads in the 50s. If heat is out during hard-freeze weather, open cabinet doors under sinks, let faucets drip, and treat the repair as urgent.
- Should I keep resetting the breaker to keep the heat on?
- No. One reset is reasonable, a storm or power blip can trip a breaker. A breaker that trips again is protecting you from a real electrical fault in the furnace or its circuit, and forcing it repeatedly is how components and wiring get damaged. Leave it off and call.
Need a technician now?
Swiss Air answers 24/7, upfront pricing, our No Price Change Guarantee, and honest answers even at 2 a.m.