Heat Went Out at Night: What to Check Before You Call

First: is anyone in danger?

Before you touch the furnace, take ten seconds for this.

• If you smell gas (many people describe it as rotten eggs), don’t flip light switches, don’t try to relight anything and don’t use your phone inside. Get everyone out. Call NIPSCO’s emergency line or 911 from outside or from a neighbor’s house.
• If a carbon monoxide alarm is sounding, get everyone and the pets out into fresh air right away and call 911. Don’t go back in until the fire department says it’s safe. Headaches, dizziness or nausea in more than one person at once is also a reason to leave.

Those calls come first. After the house is safe, call us.

If neither of those is happening, take a breath. Most middle-of-the-night heat outages come down to something simple or a single failed part.

Check the thermostat

It sounds too easy, but it’s the first thing we ask about on every night call.

• Is it set to HEAT, not OFF or COOL?
• Is the setpoint a few degrees above the current room temperature?
• Is the screen blank or dim? Replace the batteries if it uses them.
• If it runs on a schedule, did it switch to a low overnight setting you forgot about?

Bump the temperature up three to five degrees and wait a few minutes. Many furnaces take a minute or two to start the blower after the burners light.

Check the power

A furnace is an electrical appliance, even when it burns gas.

• Find the furnace power switch. It looks like a regular light switch, often on the wall or ceiling near the furnace, sometimes with a red cover plate. Make sure it’s on. It’s easy to bump by accident.
• Check your electrical panel for a tripped breaker labeled furnace or HVAC. If it’s tripped, reset it once. If it trips again, leave it off and call us.

Check the filter and the blower door

A badly clogged filter can make the furnace overheat, and a safety switch shuts it down. Pull the filter and look. If it’s gray and packed, swap it if you have a spare. If you don’t, running briefly without one to get through the night is better than no heat, but put a new one in first thing.

Then look at the furnace’s lower door. Most furnaces have a safety switch that keeps them off if that door isn’t fully seated. Make sure it’s clicked in all the way.

Check the vent pipes outside

If your furnace vents through white PVC pipes on the side of the house, go look. After a lake-effect storm or a windy night, snow and ice can pack those pipes, and the furnace won’t run. Clear them gently by hand. Don’t use tools that could crack the pipe.

Try one reset

Turn the furnace off at the power switch, wait about a minute, and turn it back on. That clears a lockout. Watch and listen: you should hear the small inducer fan, then the burners light, then the blower start.

If it doesn’t start, or starts and quits again, stop. Resetting over and over won’t fix a failed igniter or flame sensor. For more on that, read why a furnace won’t light.

Keeping the house warm safely while you wait

• Close doors to rooms you aren’t using and gather everyone in one room.
• Layer up with blankets, sweaters and hats. Put kids and older family members in the warmest spot.
• Close curtains and blinds to hold heat in.
• If you use an electric space heater, plug it straight into a wall outlet, not an extension cord, and keep it at least three feet from beds, curtains and anything that can burn. Never leave it running unattended or while everyone sleeps.
• Never use a gas oven, stovetop, charcoal or gas grill, camp heater or generator to heat the house. They can fill a home with carbon monoxide. Generators belong outside, well away from doors and windows.
• On very cold nights, open cabinet doors under sinks on outside walls so pipes get some room air.

What to tell us when you call

A few details help us figure out what’s going on before a tech even leaves, and sometimes they solve it over the phone.

• What the thermostat says and whether the screen is on.
• What you hear at the furnace: nothing, a hum, clicking, a glow, a flame that starts and stops.
• Whether there’s a blinking light on the furnace control board and how many blinks.
• Whether your stove or water heater is working.
• About how old the furnace is, if you know, and whether it vents out a chimney or through white plastic pipes.
• Who’s in the house. If there’s a baby, an elderly parent or someone with health needs, say so.

Then call. A real person answers 24/7.

Call (219) 555-0142. Day or night, weekends and holidays, a real person picks up. We’ll ask what the furnace is doing, walk through anything you haven’t tried, and tell you the visit cost before we send a tech.

When we get there, we find what failed and write the repair price down before any work starts. Our techs aren’t on commission, and “it’s old” isn’t a diagnosis. A midnight no-heat call usually ends with one part, not a new furnace.

We’re based in Munster and cover about 20 miles around. See furnace repair in Munster, furnace repair in Hammond, or the full service area. For more on our furnace work, go to furnace repair. If the furnace is running but the air is cool, read why a furnace blows cold air.