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Furnace fan keeps running with thermostat off

furnace fan

A common HVAC problem that many homeowners deal with is when the furnace fan keeps running after the thermostat has been turned off.

In addition to being inconvenient, it poses questions regarding possible system deterioration and higher utility costs as a result of reduced energy efficiency, which is why it's imperative that this problem be resolved quickly in order to reduce these concerns and prevent further damage from happening. 

There are many factors that could be causing this, and if this is something you're currently dealing with, know that you're not alone and there are ways to fix this. If you want to learn more about why your furnace fan keeps running even after the thermostat has been turned off, keep reading.

Common Culprits for Running Fans

As we said before, there are numerous reasons why your furnace fan might run constantly. Here is a closer look at some of these culprits and how you can go about trying to fix them:

Faulty thermostat

  • Check the thermostat settings to ensure the thermostat is set to the temperature you want.
  • Make sure the furnace thermostat and fan setting is set to the auto setting or is off.
  • If necessary, change the batteries in the thermostat.

Broken furnace fan limit switch:

  • Find the fan limit switch next to the burner component of the furnace, which is located inside the unit compartment.
  • Try to turn the furnace fan limit switch back on from the manual setting.
  • Seek expert help if the problem continues once the furnace fan limit switch has been activated.

Issues with electric thermostat wiring

  • A professional electrician should handle all electrical issues including, but not limited to thermostat wiring.

Failure of the furnace blower motor fan relay

  • Inspect the furnace fan relay for indications of wear or burnt marks.
  • Seek expert aid when dealing with complicated relay system problems.
  • Beyond these troubleshooting steps, homeowners can also try resetting their entire heating system by switching off power.
  • Start by finding the power switch for your furnace. This switch is usually located on or near the furnace itself. In some cases, there may be an actual power switch on the side or bottom of the furnace. Try to give the furnace some time to cool down before attempting to restart it. After waiting for a few minutes, you can turn the power back on by flipping the power switch to the "On" position or plugging the furnace back into the outlet. 
  • Lastly, adjust the thermostat to your desired temperature setting and see if the furnace fan continues to run.  

When to Call a Professional if the Furnace Fan is Still Running

While there are some troubleshooting steps homeowners can take with their thermostats and furnaces, most scenarios require a professional diagnosis and repair that should only ever be conducted by an individual who is qualified to do so. Here is a closer look at when you should reach out to a professional HVAC company like the team from Boonstra Heating and Air Conditioning:

Complex electrical issues

  • If homeowners discover complex wiring problems rather than just loose connections, professional assistance is probably needed to safely resolve these.
  • To prevent potential risks, electrical problems, particularly those involving relays or control boards, require the expertise of a qualified technician.

Broken thermostat

  • If trying to reset the thermostat or change the batteries doesn't work, a professional diagnosis is required.
  • A broken thermostat could be a sign of internal issues that a homeowner lacks the skills or resources to address.

Limit switch calibration 

  • In the event that DIY solutions are unsuccessful in stopping the furnace fan from running, an experienced technician can repair or calibrate the limit switch to guarantee proper operation.
  • If there are problems with the heat exchanger or related furnace parts, a professional assessment may also be necessary.

Issues where specialized tools and equipment are needed

  • Certain furnace parts, such as the control board or heat exchanger, can need specific instruments or diagnostic devices that most homes don't have.
  • Experts have the ability to recognize and handle problems related to these elements precisely.

When to call Boonstra Heating and Air Conditioning:

DIY methods fail

  • It is essential to contact an experienced HVAC specialist if DIY tweaking fails to fix the issue or if concerns continue. This could indicate that your thermostat needs to be replaced.
  • Fixing complex issues without having the appropriate expertise could result in further harm or safety risks.

 Safety issues

  • Any problems with gas lines, electrical components, or other fire threats need to be resolved by an expert, especially if things need to be replaced.
  • Professionals with the know-how to manage these circumstances safely include those at Boonstra Heating.

Age and upkeep of the furnace

  • Complex problems may arise from older furnaces or from ones that don't receive routine maintenance.
  • Expert technicians are able to evaluate the system's overall state and suggest necessary replacements or repairs.

Ultimately, regular professional maintenance can prevent issues before they arise, ensuring your furnace operates efficiently for as long as possible. Our certified HVAC technicians are able to provide homeowners with comprehensive inspections and address any issues before they become more severe and costly.

Count on Boonstra for Accurate Diagnostics and Repairs

Are you having trouble with your thermostat and furnace fan? If so, the professional and experienced team from Boonstra Heating and Air Conditioning is here to help you get your HVAC system back up and working correctly in no time.

For all repair and maintenance services, the certified technicians from Boonstra are available 24/7/365 days a year, including after-hours, weekends, and holidays, at no extra cost.

Boonstra Heating and Air Conditioning is pleased to serve homeowners throughout Hamilton, Brantford, Kitchener, Burlington, Oakville, Cambridge, Ancaster, Binbrook, Brant, Caledonia, Campbellville, Carlisle, Dundas, Flamborough, Freelton, Kilbride, Lowville, and Millgrove. If you live in any of these communities, reach out to our team over the phone or schedule your repair appointment directly online using our booking form.

We look forward to partnering with you!

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