If this is your first house, nobody ever showed you where the furnace switch is. That is not a failure on your part. Work down this list first — a good share of “dead” furnaces are one of these five things, and all five are free to check. If none of it works, we will come out.
First, the safety one
If you smell gas, or a carbon monoxide alarm is going off: get everyone out of the house first, then call 911 from outside. Do not flip any switches on your way out. This is the one situation where you do not troubleshoot anything.
1. Find the furnace switch
There is a light switch on or beside the furnace, usually at the top of the basement stairs or on a joist nearby. It looks exactly like a normal light switch and it is very easy to knock off while carrying laundry. If it is off, flip it on and give the furnace five minutes.
2. Check the breaker
Open your electrical panel and look for a breaker that sits between on and off, or is labelled furnace. Push it all the way off, then all the way back on. If it trips again right away, stop — that one is ours, not yours.
3. Check the thermostat
Make sure it is set to Heat and not Cool or Off, and that the target temperature is above what the room actually is. If the screen is blank, it takes batteries — usually two AAs behind the faceplate. A dead thermostat looks exactly like a dead furnace.
4. Look at your filter
Pull the filter out. If you cannot see light through it, that is your problem, and a clogged filter can shut a furnace down on its own safety switch. Any hardware store has them. Write the size on the furnace in marker so you never have to guess again.
5. Check the furnace door
The front panel has a safety switch behind it. If the door is not seated properly the furnace will not run at all, by design. Push it firmly until it clicks.
If it is still not running — protect the house
- Open the cabinet doors under kitchen and bathroom sinks so warm air reaches the pipes
- Run a pencil-thin trickle of cold water from the faucet furthest from your water heater
- Close off rooms you are not using and put a towel along the bottom of the door
- Do not use the oven or a gas range to heat the house. That is how people end up with carbon monoxide poisoning
- A space heater is fine, but plug it straight into the wall — never into a power strip or extension cord
Then call us
If you worked through all five and it is still dead, that is genuinely a repair and there is nothing else for you to try. Call (920) 304-9377 — for a house that is actually getting cold we want you on the phone, not filling in a form.
You Are Not Going To Break It
Every one of those five checks is something a homeowner is meant to be able to do. You cannot damage the furnace by flipping its switch, resetting a breaker, changing a filter or closing the door properly. The worst case is that none of it works and you have lost two minutes.
Service Area
We cover Green Bay, De Pere, Ashwaubenon, Howard, Suamico, Bellevue and Allouez, plus Brown County and eight surrounding counties across Northeast Wisconsin. See the full service area →
Why We Wrote This Down
Plenty of shops would rather you did not know that a furnace switch exists, because a trip charge for flipping one is easy money. We would rather you fixed it yourself for free and remembered who told you how. When something genuinely breaks — and eventually it will — you already know who to call.
Frequently Asked Questions
How do I know if it is the thermostat or the furnace?
Turn the thermostat up five degrees past room temperature. If you hear nothing at all from the furnace within a minute or two, and the thermostat screen is blank or unresponsive, start with thermostat batteries before assuming the worst.
My furnace turns on and then shuts off after a minute. What is that?
Starting and stopping in short bursts usually means it is overheating and shutting itself off on a safety, and the most common cause is a blocked filter. Change the filter first. If it keeps doing it, stop and call us — that one needs a look.
Is it safe to run a space heater overnight?
One heater plugged straight into a wall outlet, on a hard floor, well away from bedding and curtains, is reasonable for a night. Never run one through a power strip or extension cord, and never use a gas range or oven to heat a room.
What does it cost to find out what is wrong?
A diagnostic visit is $125 plus tax, and that is what it costs to have a licensed contractor tell you exactly what is wrong and what the repair will run before anything gets touched. Quotes on a new system are free.
How fast can you get here?
Call and we will tell you honestly, on that call, rather than promising a window we cannot hold. Club members go to the front of the line.
Prefer to talk? Call (920) 304-9377