What to Do if Your Heater Isn’t Working

Woman clutching pillow in heavy winter coat sitting on couch at home, and looking unhappy. "What to Do When Your Heater Breaks Down"

In case you’re reading this because it just happened to you, we’ll cut to the chase: here are the things you should check if your heat isn’t working.

Digital thermostat

The Thermostat

First of all: double-check your thermostat. Is the temperature set high enough for it to trigger the furnace? If your thermostat is non-digital, is the heat switch engaged? Make sure you set the thermostat to the right temperature and that the heat switch is on. It’s a good idea to double-check the settings even if you just programmed them, because when some thermostats lose power, they default back to their factory settings.

If your thermostat requires batteries, replace them now, then check the settings again. If you can’t find a place to install batteries, your thermostat is attached to your home’s internal electricity. Try to turn on other electrical appliances nearby. If they aren’t working either, you either blew a fuse or have a power outage.

Next, make sure your thermostat is communicating with your furnace. Turn on the furnace fan using a switch on the thermostat. All the fan needs to run is electricity, so If you don’t hear it come on, it means your furnace is not receiving power. Never set your thermostat at 90 degrees. That’s hot enough to activate the furnace the moment you have it working again, so you’ll know when you can stop looking for the problem.  


Circuit breaker box

The Circuit Breaker

All furnaces require electricity to operate, even if the fuel source is propane or natural gas. If either the fuse in charge of your furnace or your thermostat have blown, then your heat won’t work. Find your main power distribution panel or circuit breaker panel. The panel will probably be in your basement or garage. Look for the breakers that send power to the HVAC unit and the thermostat. If these have popped off, reset them back to the On position, then check to see if doing so solved the problem.

Do not reset a broken circuit more than once. Forcing a connection runs the risk of causing damage to your system, your appliances, or yourself! If the circuit breaker isn’t the problem and you aren’t getting power anywhere, call your electrical company.

If the main circuit doesn’t seem to be the problem and you have power elsewhere in your house, check for a furnace switch. A lot of furnaces have redundant circuit breakers built into or near them. Sometimes they look like regular light switches. It can be really easy to accidentally turn off the furnace this way, and you wouldn’t notice until it starts to get cold. Look for a furnace switch and make sure it’s on.


furnace pump

The Condensate Pans

If you still haven’t found the problem, it’s time to start troubleshooting the furnace itself. To start, look for your furnace’s drain pans (or, condensate pans). The condensation produced by furnaces contains acid which can damage the system. To prevent this, most furnaces have a float switch and a condensation pump. The float switch and drain or pump safely remove condensation from the furnace and into the drain pans.

Check the drain pans to see if they contain standing water. If they do, check either your furnace’s drain or condensation pump. If the pan has a drain, you’ll see PVC piping coming out of your furnace. Check to make sure the drain is unblocked and clear so that the condensation can flow through it. Drain the fluid from the pan and try to start your furnace again. If your furnace has a pump, you’ll see a mechanical pump at the bottom of a water line drawn into the side of the pan.

Your furnace may also have a collection reservoir with a tube feeding down into it. Check this reservoir for the float switch. A float switch measures how much condensation is in the reservoir. When too much condensation builds up, the float switch triggers and the furnace won’t turn on. Hold the float under the activation point (indicated by the waterline) to verify if this is the problem. If the furnace turns back on after about a minute, it means your furnace is building up too much condensation. You probably need a new condensation pump or drain. Wash your hands after handling the pump, drain, or float switch and give us a call.


Homeowner replacing air filter

The Air Filter

Your HVAC keeps dirt and other substances from circulating through the air it treats by processing it through an air filter. This filter catches and collects the debris that builds up. Air filters require periodic replacement, or the debris they collect will build up and eventually clog air from passing through your vents. Not only will this make the air in your home dirty, it can strain your furnace and cause overheating.

As a safety feature, some furnaces will turn off when they have to work too hard to push air through the vents. That means if you haven’t replaced your air filter recently, it could be the causing the heating failure. Pull out the air filter. Replace it immediately If it’s discolored, opaque, or covered in filth. You should change your Air filters once every three months, or more often depending on your home’s age and air quality.


Propane Tank

Motor and Power Supply

If your furnace is 20 years old or older, check to see if the pilot light is on. If it isn’t, see the instructions in your owner’s manual for instructions on how to relight it. Check the internet for instructions for your furnace’s particular brand and make if you don’t know where the owner’s manual is.

After checking the pilot light, you’ll want to check your blower motor. Most modern furnaces have a small plastic window on the side of the housing. It’ll be dark inside this window, but you should be able to see the blower motor’s indicator light. If the motor is working properly, the light will be blinking green intermittently. If it’s doing anything else, that means something’s wrong with the motor. Fixing a heater’s motor is a job best left to experts, so if the light isn’t blinking green, give us a call ASAP.

The last thing you should check is your furnace’s power supply. Most furnaces in America use natural gas. If the furnace isn’t working it could be having trouble getting to the natural gas it needs to ignite. Even worse, your home could have a gas leak. Turn on another gas-burning appliance such as the stovetop. If your stove isn’t working either, you’ve found the culprit. Call your gas company immediately to check for a gas leak and get your propane tank refilled.


The most important thing you can do in case of a heat failure is to call an expert fast. Furnace problems are no joke, especially during a Minnesota winter, so if you suspect a problem, schedule a maintenance check-up right away. The best way to prepare for heating failure is to make sure it doesn’t happen in the first place. If you’re interested in more tips for keeping warm this winter, check out our blog on how to save money on heating, or check out our partner Blue Ox Heating & Air’s blog for tons more info. Stay warm!

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