Why Does My Furnace Fan Keep Running? Quick Fixes And Tips

Rima Chatterjee


Is your furnace fan running continuously? It could be due to a thermostat, switch, or air handler issue. The fan limit switch may be improperly set. Here are ways to troubleshoot and fix this problem:

  1. Check your thermostat’s settings. Make sure it’s on auto mode, not continuous fan mode. Increase the temperature a few degrees. See if the system shuts off automatically.
  2. Also, take a look at the fan limit switch. This part controls when the blower fan runs in relation to heating cycles. If it’s not set correctly or is malfunctioning, the fan won’t stop. Check for shorted wires or disc issues.
  3. If you still can’t find a solution, call a professional HVAC service tech. They have the knowledge and skills to solve complex HVAC issues. Don’t let your bank account take the heat. These are the common culprits behind a furnace fan that won’t quit.

Common Causes of a Furnace Fan That Keeps Running

Why Does My Furnace Fan Keep Running

Is your furnace fan running continuously? Check the switch on your thermostat is set to “auto” and not “on”. If it’s still running, the issue might be with your furnace fan limit switch or control board.

  • A faulty blower motor or relay could be the cause of HVAC issues.
  • Check if the time delay has been set for an extended period.
  • Cleaning and inspecting the unit can reveal simpler problems such as dirty filters, ductwork obstructions, or wiring connections.
  • To avoid future issues, consider setting up regular maintenance service from an HVAC contractor.
  • If you’re using a smart thermostat, ensure it’s compatible with your HVAC system and programmed correctly for optimal performance.

Don’t ignore ongoing problems with your HVAC system – act fast to prevent costly repairs. Stay warm!

Troubleshooting Steps to Fix the Furnace Fan That Keeps Running

Frustratingly, your furnace fan can keep running. Here’s a 5-step guide to help fix it!

  1. Check the Thermostat Setting. Make sure it’s set to ‘auto’ or ‘heat’.
  2. Check the Fan Switch on the Air Handler. Turn off any manual override switch or check the ‘HEAT’ switch on the control board.
  3. Inspect the Fan Limit Switch. Look for a disc-shaped switch near the blower motor. It should be set at 90-115°F (32-46°C).
  4. Check for Shorted Wires. A bad/shorted thermostat wire can cause the fan to run continuously.
  5. Call an HVAC Service Tech. If the problem persists, call a technician for help.

Plus, modern smart thermostats can cause this issue if not installed correctly. And one homeowner had to replace their fan limit control to fix their running fan. So, if you’re stuck with a running fan, just think of it as a great soundtrack for your indoor marathon.

How to Override the Fan Limit Control Switch?

Fed up with your furnace fan running all the time? It’s likely a problem with the fan limit control switch, regulating the blower’s activity. Not to fear, here’s how to override the switch:

  • Track down the Fan Limit Control Switch: It will be in the air handler’s furnace hood or on the heating system’s control board. It has a white button/knob labeled “manual override.”
  • Shut off the Heating Cycle: To prevent any damage, turn off the heat or set the thermostat to “cooling” mode.
  • Push the White Button: Hold it down for one minute until you hear a click. This shows you have overridden the fan limit control, allowing the blower to keep running until you switch it off.

If this doesn’t work, it could be a shorted wire or other issue. Get help from an experienced HVAC service tech.

Don’t ignore this issue, as it could cause more problems with your system and increase your energy bills. Take action now and reclaim your peace and quiet!

When to Call a Professional and How to Get Help for Furnace Fan That Keeps Running

Troubleshoot your furnace fan before calling a professional:

  • Ensure the thermostat switch is on “auto” and the fan setting is set to “auto.
  • If the switch is “on,” the fan will keep running after the heating cycle.
  • Inspect your air filter for debris and clean it.
  • Look for any shorted wires or problems with the circuit board, relay board, or fan limit control.

For more complicated issues, contact an HVAC expert who can help diagnose problems with:

  • Controls
  • Wiring
  • Motor
  • Blower fan
  • Limit control switch

Consider using a smart thermostat that can alert you when something’s wrong with your HVAC system. Honeywell offers models with this feature.

Visit the Inspectapedia website for more information and tips on maintaining furnaces and air conditioners.

Why wait? Troubleshoot now to keep your home warm and your fan running!


To stop your furnace fan from running continuously, you must find the problem and fix it. It could be a faulty thermostat or fan switch. Or the limit switch or thermostat setting is wrong. Check the furnace controls and wiring for shorted wires too. Reset the circuit board. Check the dip switches. Make sure the limit control is right. You might need help from professionals. To avoid such problems in the future, keep your HVAC system in good shape. Change filters regularly. Inspect burners, air handlers, heat exchangers, and other parts. This will keep your system good and prolong its life.

About the author

Debarghya Roy: A heating systems author, Passionate about energy efficiency and sustainability, Sharing insights and empowering readers through informative blog articles.