Furnace not heating? Here’s how to fix it

If your furnace isn’t heating, it can be a pretty frustrating problem, especially when you need it the most. But before you start calling in professionals, there are a few simple things you can check yourself. Whether you have a gas or electric furnace, some basic troubleshooting steps could help you pinpoint the issue and get your home cozy again. Let’s dive into some DIY fixes you can try yourself.

The info in this piece might not match your exact appliance model. We try to dish out helpful advice for all sorts of DIY fixes, but different models and setups can mean different troubleshooting steps, error codes, part swaps, and so on. For the best guidance, it’s a good idea to peek at your appliance’s manual or give us a shout if you’ve got questions.

Check the thermostat settings

The thermostat is often the first place to check when your furnace isn’t heating. If the thermostat isn’t set correctly, it can prevent the furnace from kicking on.

1. Make sure the thermostat is set to “heat” mode.
2. Adjust the temperature setting to be higher than the current room temperature.
3. If your thermostat uses batteries, replace them with fresh ones.
4. Reset the thermostat to see if it resolves any glitches.

Once the thermostat is correctly set and functioning, you can rule out this simple cause and move on to more complex checks. 

Inspect the power supply (for electric furnaces)

If your electric furnace isn’t heating, it could be a power issue. A lack of power could be as simple as a tripped breaker or a flipped power switch.

1. Check the furnace’s power switch to make sure it’s in the “on” position.
2. Go to your electrical panel and inspect the circuit breaker. If the breaker for the furnace is in the “off” position, flip it back on.
3. Use a multimeter to check that the furnace is getting power. Test the voltage at the furnace’s power connection or outlet to confirm.

If power is restored, your furnace should start heating. If the breaker trips again, there may be a deeper electrical issue. 

Check the gas supply (for gas furnaces)

For gas furnaces, no gas means no heat. If your furnace isn’t turning on, it’s important to make sure that the gas supply is properly connected and functioning.

1. Check the gas valve to ensure it is in the “open” position.
2. If your furnace has a pilot light, check to see if it is on. If it’s out, relight it following the manufacturer’s instructions.
3. If you’re not able to relight the pilot light, you can test the gas valve with a multimeter to check for proper voltage and functionality.

If the gas supply is fine and the furnace still doesn’t heat, you might need to inspect other components like the ignition system.

Inspect the furnace’s filter

A clogged air filter restricts airflow, causing your furnace to overheat and shut off the burners. The result? Cold air blowing from your vents. Swapping out your air filter every 1-3 months can prevent this issue and improve your indoor air quality.

1. Locate the air filter compartment, usually near the blower or return air duct.
2. Gently remove the old filter by sliding it out.
3. Check the size printed on the filter frame and get a matching replacement.
4. Insert the new filter, making sure the airflow arrows point toward the furnace.
5. Close the filter compartment and turn the furnace back on.

Read more: 12 simple space heater safety tips for this winter

Examine the furnace blower motor

The blower motor is responsible for circulating warm air throughout your home. If the motor isn’t working, the furnace might be running, but you won’t feel any heat.

1. Listen closely to the furnace to see if you can hear the blower motor running. If you don’t hear it, it could be the issue.
2. Use a multimeter to check the motor for continuity. If the motor doesn’t have continuity, it’s faulty and likely needs to be replaced.
3. If the motor does have continuity, check the capacitor and wiring to make sure they’re not causing issues.

If the blower motor is the problem, it will need to be replaced to restore heating. If you’re unsure about testing electrical parts, we have more tips on using a multimeter in our repair help section.

Inspect the limit switch

The limit switch is a safety feature that prevents the furnace from overheating. If it’s faulty, it can stop your furnace from heating, even if everything else seems fine.

1. Look for the limit switch near the burner assembly or furnace compartment.
2. Use a multimeter to test the limit switch for continuity. If there’s no continuity, it may be defective and need replacing.
3. If the limit switch is tripped, it might be caused by a clogged filter or poor airflow, so make sure the air filter is clean and airflow is unobstructed before replacing the switch.

Read more: 12 things you should know about portable space heaters

Check the heating element (electric furnaces)

For electric furnaces, a faulty heating element is a common reason why the furnace isn’t producing heat. If the element is damaged or broken, it won’t be able to generate warmth.

1. Turn off the furnace and remove any access panels to reach the heating element.
2. Use a multimeter to check for continuity in the heating element. If there’s no continuity, the element is broken and needs to be replaced.
3. If the element seems intact but still isn’t heating, check the wiring and connections for any loose or burnt spots that might be affecting its operation.

Examine the ignition system (gas furnaces)

In gas furnaces, the ignition system is responsible for lighting the gas burners. If the ignition system fails, your furnace won’t be able to produce heat.

1. Check the ignition system, including the igniter or pilot light. If the pilot light is out, try relighting it following the furnace’s manual.
2. Use a multimeter to test the igniter for continuity. If it has no continuity, it’s faulty and should be replaced.
3. For electronic ignition systems, check the control board and flame sensor to make sure they’re working properly. If the flame sensor is dirty or damaged, it may prevent ignition.

Read more: Your guide to choosing a space heater

Staying warm

We hope these tips help you get the heat back on. For all your furnace parts and maintenance needs, swing by AppliancePartsPros.com. We’re here to provide quality parts and advice you can count on.

Follow us on Facebook and Twitter for more tips and updates. If you’ve got questions or need a hand, reach out anytime. We’re always happy to help you keep your home warm and comfy.