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No heat

When the heat stops in cold weather, a few simple checks solve a surprising share of calls. Some signs, though, mean leave the house first and call from outside.

By the Wolfpack Home Services editorial team · Reviewed · How we research

Do this now

  1. If you smell gas, leave the house immediately and call your gas utility or 911 from outside. Do not switch anything on or off.
  2. If a carbon-monoxide alarm is sounding, get everyone outside and call 911.
  3. Otherwise: check that the thermostat is set to heat, set above room temperature, and has working batteries.
  4. Check the furnace or boiler switch (it looks like a light switch) and the breaker, and replace a clogged filter.
  5. For oil or propane heat, check the tank gauge.
  6. If it still will not run, call an HVAC contractor. Use space heaters carefully — away from anything that burns, plugged directly into the wall, never left unattended.

What usually causes it

  • A dirty filter causing the furnace to overheat and shut itself off
  • A failed igniter or dirty flame sensor
  • A tripped breaker, blown fuse or switched-off service switch
  • An empty oil or propane tank
  • On high-efficiency furnaces, a blocked intake, exhaust or condensate drain

What a professional will do

A technician reads the fault code, tests the ignition sequence and safety switches, and checks combustion and venting, including a carbon-monoxide test on fuel-burning equipment. On an older system they should tell you plainly whether a repair is sound or whether you are approaching replacement.

How to prevent it

  • Change the filter on the schedule the manufacturer recommends
  • Have fuel-burning equipment serviced every fall
  • Keep intake and exhaust pipes clear of snow, leaves and nests
  • Install carbon-monoxide alarms on every level and test them

Rules and paperwork in Pennsylvania

  • Pennsylvania’s Home Improvement Consumer Protection Act requires most contractors who perform home improvements to register with the Attorney General’s office and to give you a written contract for any job over $500. The registration number belongs on the estimate and the contract — ask for it.
  • Technicians who handle refrigerant must hold EPA Section 608 certification under the Clean Air Act.
  • Pennsylvania does not issue a statewide license for this trade. Some municipalities register or license it locally, which is one reason to confirm requirements with your own municipality.

Sources: Pennsylvania Office of Attorney General — Home Improvement Consumer Protection Act; U.S. EPA — Section 608 Technician Certification; Pennsylvania Department of Labor & Industry. Rules change — confirm current requirements with the agency and with your municipality.

Frequently asked questions

My furnace runs for a minute and then shuts off. Why?

Short cycling like that is commonly a dirty filter, a dirty flame sensor, or a blocked vent. Replace the filter first; if it continues, it needs a technician.

How do I keep pipes from freezing while the heat is out?

Open cabinet doors on outside walls, let faucets drip, and keep interior doors open so warmth circulates. If the outage will be long, shut off the water and drain the lines.

Is it safe to heat with the oven?

No. A gas oven can produce carbon monoxide, and any oven left open is a burn and fire hazard.

Go deeper

Our full heating & cooling guide covers how the work is done, what affects the price, and what to ask before you hire, and there is more on furnace repair.

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This guide is general information, not a substitute for a professional assessing your home. If you are unsure whether something is safe, treat it as if it is not.