No Heat in House? 10 Steps to Check Before You Call

No heat in house means your furnace, boiler or heat pump has stopped warming your home, whether it will not start, runs without heating, or shuts off on its own. Many causes are simple: a thermostat setting, a tripped switch, an empty oil tank or a clogged filter. Here are 10 steps to work through, in order, before you call, plus the safety signs that mean stop and get help now.

Key Takeaways

• Safety first. Gas smell or CO alarm: leave the house and call the gas company or 911.
• Start with the thermostat. Mode, setpoint and batteries cause many no-heat calls.
• Check power and fuel. Switches, breakers, gas service and oil levels.
• Look for error codes. A blinking light tells the technician a lot.
• Protect your pipes. If heat will be off for a while, keep water lines from freezing.

1. Rule Out a Safety Problem

• If you smell gas, leave the house now. Do not flip switches. Call the gas company or 911 from outside.
• If a carbon monoxide alarm sounds, get everyone out and call 911.
• If you see smoke, soot puffing from an oil burner, or water pouring from the boiler, shut the system off and call for service.

Soot and a yellow flame can point to a cracked heat exchanger. Do not run a furnace you suspect is unsafe.

2. Check the Thermostat

• Set it to Heat, not Cool, Off or Auto.
• Raise the setpoint 3 to 5 degrees above room temperature.
• Replace the batteries if the screen is dim or blank.
• Check for a schedule or hold that is overriding you.

Still nothing? See our guide to a thermostat not working.

Want help right away? Request a no-heat repair visit and send a photo of any error code or blinking light.

3. Check Power to the Heating System

• Find the furnace or boiler emergency switch, often a red-plate switch at the top of the basement stairs. Make sure it is on.
• Check the breaker panel for a tripped breaker. Reset it once. If it trips again, leave it off and call.
• On furnaces, make sure the front door panel is fully closed. A safety switch keeps the furnace off when it is open.

4. Check Your Fuel

• Gas: are other gas appliances working? If none are, call the gas company.
• Oil: check the tank gauge. Running out can also clog the filter and air-lock the line. See oil furnace problems.
• Propane: check the tank level.

5. Replace a Dirty Filter

• A clogged furnace filter can overheat the furnace and trip its safety limit.
• Swap it, wait a few minutes and try again.
• Per DOE's air conditioner maintenance checklist, a clean filter can lower energy use by 5% to 15%, and the same filter serves your furnace.

6. Read the Error Code

• Most furnaces have a small LED behind a window in the lower door. Count the blinks.
• The code chart is usually on the inside of the door.
• Boilers and heat pumps often show codes on a display.
• Take a photo before you reset anything.

7. Press Reset Only Once

• Oil burners have a red reset button. Press it once. If the burner does not light, stop.
• Repeated resets can flood the chamber with oil and cause a puffback.
• Gas furnaces may reset by cycling power for 30 seconds.

8. Check What the System Is Doing

• Furnace will not start: see furnace not turning on.
• Runs but blows cool air: see furnace running but not heating.
• Burner lights but no air moves: see furnace fan not working.
• Boiler home, some rooms cold: see no heat in one zone and common boiler problems.
• Heat pump blowing cool air: see heat pump blowing cold air.

9. After a Storm or Power Outage

Nor'easters knock out power across the North Shore. When it comes back, systems sometimes stay locked out. See no heat after a power outage for restart steps and generator safety.

10. Keep the House and Pipes Safe While You Wait

• Close doors to unused rooms and keep curtains shut.
• Use space heaters safely: UL-listed, plugged into a wall outlet, 3 feet from anything that burns.
• Never use an oven, grill or camp stove for heat.
• Drip faucets and open sink cabinets on outside walls. See how to keep pipes from freezing without heat.

Renting? Massachusetts has rules about the heat landlords must provide. See no heat in an apartment in Massachusetts.

What Should You Tell the Technician?

In our experience with North Shore homes, a few details shorten the visit and often the bill. Have these ready when you call:

• Your system type: gas or oil furnace, hot-water or steam boiler, or heat pump.
• What it is doing: silent, clicking, humming, running but cold, or starting then stopping.
• The error code or blink pattern, with a photo.
• When it started and anything that changed, like a storm, filter change or oil delivery.
• The approximate age of the system, from the data plate if you can see it.

A common problem we see after the first cold snap is a dirty flame sensor or igniter on a furnace that sat idle all summer. A fall tune-up catches these before you need heat.

When to Repair, When to Replace

Most no-heat calls are repairs: igniters, flame sensors, capacitors, filters or controls. If your system is old and failing often, compare options in furnace repair or replace. Per DOE's guide to furnaces and boilers, older low-efficiency systems often run at 56% to 70% AFUE, while new condensing units reach 90% to 98.5%. As of 2026, a yearly heating tune-up is still the best way to avoid a no-heat night.

Get Your Heat Back On

No heat in house usually comes down to the thermostat, power, fuel, a filter or a failed part. Work through the basics safely, then call with the error code in hand.

Jose has worked in HVAC since 2015 and repairs furnaces, boilers and heat pumps across the North Shore. HomePros gives a written flat price before any repair starts. Schedule heating repair, or call (781) 426-8428. More in our furnace and boiler replacement guide.