Furnace Blower Not Working

When your furnace blower/furnace fan is not working, your comfort level decreases. Learn about some common furnace blower fan problems, what may be causing them, and what you can do to get your house as warm and toasty as it should be.

Your gas furnace burns fuel to produce heat. That heated combustion gases then pass through a heat exchanger, warming the outer surface. (Newer condensing furnaces have a secondary heat exchanger for greater efficiency.) The blower fan pulls cool air from the return ductwork and passes it over the heat exchanger(s), warming it. The blower then forces the heated air into the supply ductwork and distributes it through your home.

But the blower motor and blower fan don’t take summer off. When paired with a central AC unit or a heat pump, the blower assembly distributes cool air through your home after it has passed over the evaporator coil.

The fan doesn’t shut off at the same time as the furnace or AC unit does. The furnace fan motor will keep the fan running typically for one to five minutes after a heating or cooling cycle to distribute the heated or cooled air and help maintain an even temperature throughout your home. 

As you can see, the furnace blower assembly works hard. But what do you do if there’s a problem? Come here to find troubleshooting ideas and potential fixes, of course. Let’s get started.

If the furnace fan keeps running, there could be several things at play. But if the furnace fan keeps running with the thermostat off, that may be an electrical issue with the thermostat, a fan limit switch, the blower motor, or the furnace control board.

The solution will be based on the cause.

Solutions: If the furnace blower won’t turn off, check the thermostat. Make sure the thermostat fan setting is set to Auto rather than On. If it’s set to On, the fan will run continuously, even when the furnace is not producing warm air. This makes it seem as if the furnace fan won’t shut off.

If the furnace fan keeps running with the thermostat off, try taking the faceplate off of the front of the thermostat. Does the furnace fan shut off? That tells you the thermostat is the likely issue. You may need new batteries or need to check the wiring. Or you may need a new thermostat.

If thermostat troubleshooting doesn’t work, check the filter, and change it if it’s dirty. A clogged filter can restrict airflow to the furnace making it run nonstop. However, a clogged filter can also cause a safety switch to trip to prevent the furnace from overheating, shutting it down. Also, make sure the return air vents aren’t blocked.

If neither the thermostat nor a dirty filter is the issue, it’s time to call your local HVAC company for help. They’ll determine if a safety switch, the blower motor, the furnace control board, or some other component is causing the problem.

If your blower turns on and off repeatedly before the heating cycle is finished, there are several causes, including:

• Dirty air filter
• Blocked return air vents
• Faulty thermostat
• Limit switch issues
• Clogged furnace burner
• Dirty or corroded flame sensor

Solutions: Change the filter if it’s dirty. Go through your home and make sure couches or other furniture aren’t blocking the return air vents or registers. Check your thermostat to ensure it’s on Heat mode and the temperature is set to your desired comfort level.

If these DIY furnace troubleshooting efforts didn’t do the trick, you may need to call for furnace repair. Addressing some of the remaining issues mentioned above is best left to a trained HVAC professional.

If the furnace fan is not turning on, that means the furnace blower motor is not working. There are a few reasons this may be happening, including:

1. Thermostat set incorrectly
2. Blown fuse or tripped circuit breaker 
3. Main gas line turned off
4. Blower door removed or ajar
5. Burner does not ignite
6. Defective component
7. Lockout

For the first four items, there are easy fixes, if that is the reason for the furnace fan not turning on. Here’s what to try:

1. Adjust the thermostat to Heat and your desired temperature.
2. Replace the fuse or reset a tripped circuit breaker. If it keeps blowing a fuse or tripping the circuit breaker, call for service.
3. Contact the gas company to check.
4. Close the door to restore power to the furnace and the gas valve.
5. Call for service.
6. Call for service.
7. For a newer furnace, try turning the power on-off-on-off twice in 30 seconds.

If your troubleshooting efforts get you nowhere, your blower motor may not be working properly, but it may also be an issue with another component. Modern furnaces have internal safety features that will shut the furnace down to avoid a hazard.

Contact your local HVAC service to troubleshoot, diagnose, and fix the problem to get warm air blowing again.

If the furnace blower comes on but the furnace won’t ignite, you know it's not a problem with the furnace fan or blower motor. Rather, it’s a sign of another problem, such as an issue with the ignition system, flame sensors, or again, the thermostat,

Solutions: First, check to make sure the thermostat fan setting is set to Auto rather than On. If it’s set to On, the fan will run continuously, even when the furnace is not producing warm air. In effect, your furnace is blowing cool air.

Second, check the furnace filter and replace it if it’s dirty or clogged. Low airflow can cause the furnace to struggle to circulate warm air.

If the first two troubleshooting steps don’t solve the problem, call your local HVAC company for service. They’ll troubleshoot the issue and get you warm again in no time.

If thermostat troubleshooting,  changing the furnace filter, and unblocking blocked return air vents didn’t improve the situation, it’s probably time to call the HVAC professionals. Your furnace is a high-tech piece of equipment and needs expert troubleshooting, diagnostics, and repair.

A trained HVAC technician can handle:

• Electrical or wiring issues
• Furnace fan limit switch issues
• Furnace capacitor issues
• Blower motor issues
• And more

If the HVAC technician determines that your furnace blower motor is shot, you will need to decide between furnace blower motor replacement and furnace replacement. That’s because the blower motor is designed to last as long as your furnace.

In general, you can expect a furnace to last 15-20 years. If your furnace is 15 years old and you’re having more frequent repairs, or the blower motor isn’t the only thing that needs to be replaced, you’ll want to seriously consider getting a new furnace, or taking the opportunity to do a gas furnace to heat pump conversion.

You can get more information on making this decision in our Repair or Replace Guide.

The best way to prevent blower motor problems and other furnace issues is to take care of your furnace. Change the air filters regularly, generally every 1-3 months depending on the filter. If you have a whole-house air purification system, follow the maintenance instructions for your system.

Don’t wait until your furnace stops working to schedule a yearly furnace tune-up. Among other things, your HVAC technician will do a full inspection of your gas furnace, clean parts, and lubricate the blower motor. They can also check your thermostat and whole-house humidifier if you have one.

Opt into Trane Diagnostics for peace of mind and next-level service. Through the Trane Home App, you can give your dealer remote monitoring capabilities. Your Trane smart thermostat sends data in real-time to your dealer, notifying them when it’s time for HVAC maintenance or system malfunctions, sometimes before you even realize there’s an issue. 

They can run furnace troubleshooting tests to pinpoint a problem. Sometimes, they can even solve the problem remotely. In this situation, you would grant them one-time dealer remote access (DRA). 

If an on-site service call is required, the HVAC technician will arrive with the knowledge collected during remote access. This enables shorter service calls and ensures the technician has the proper replacement parts. 

A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

Expert review by Kimberly Sexton, Senior Systems Engineer

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