Why Is My Furnace Still Running When Turned Off?

When a furnace continues to run while turned off, it uses more energy, raises your utility bill, and can make your home uncomfortably warm. While you can fix some causes for a constantly running furnace, a professional HVAC tech can help with more complicated furnace repairs. If you’re asking, “Why is my furnace still running when turned off,” learn why and how to fix it manually from the heating repair experts in Hodgkins, IL.

Common Reasons for a Furnace That Won’t Turn Off

The most typical problems HVAC technicians see with malfunctioning furnaces include:

1. Problems with the Thermostat

Your thermostat controls the furnace by telling it your ideal room temperature and gauging when it’s time to stop running. Thermostat problems can make your furnace run continuously, so start by inspecting your thermostat.

Start by taking a look at your settings. Thermostats have settings for heat and cooling in addition to an “on” and “auto” switch for the fan. If you set your thermostat to the heat setting and have the fan turned to “on,” the fan will keep pushing heated air non-stop. Change the setting to “auto,” and the fan will only turn on when the furnace needs to heat the home’s temperature.

If your thermostat doesn’t make a difference in how often your furnace runs, something’s wrong with communications between the unit and thermostat. Often the culprit behind this lies in the thermostat wiring, requiring the services of professional HVAC repair technicians to correct safely and effectively.

2. Dirty Air Filters

A dirty air filter interrupts the heat exchange that takes place during normal HVAC operations. Your furnace blower pulls cold air through your air filter to heat it and funnel it back into your home, so a clogged filter can lengthen the process and keep your furnace running. If you’re asking, “Why is my furnace still running when turned off,” try changing out your air filter to see if that helps.

3. Electrical or Mechanical Failures

Furnaces consist of several electrical and mechanical systems that work together to create and distribute heat throughout your home. When those systems begin to fail, your furnace may run continuously to try and heat your home regardless of failing mechanical or electrical functions. Common problems that can cause a constantly running furnace include:

Broken Primary Controller

The primary controller regulates the temperature of the air that your furnace puts out. When your furnace operates with a malfunctioning or damaged primary controller, your system can’t tell when it needs to shut off.

Damaged Limit Switch

Furnaces use blowers to suck in cold air and blow out warm air, so a malfunctioning blower motor can confuse your furnace. Blower motors turn off and on according to the limit switch, a mechanism that measures the interior temperature of your furnace and tells it when to turn off. Broken limit switches won’t respond, leaving your furnace to run continuously.

4. Air Duct Issues

Damaged, clogged, or disconnected air ducts can leak hot air before it gets to your vents, resulting in a furnace that keeps working to try and meet your temperature settings. Signs that you have problems with your air ducts include:

Fluctuating Temperatures

The temperature throughout your home shouldn’t vary, so if you notice cooler or warmer rooms as you walk through your house, you may have an air duct issue.

Poor Indoor Air Quality

Leaky or disconnected air ducts can suck up dust and debris and distribute it through your vents, causing you to have to clean more often and contributing to respiratory discomfort.

Strange Noises and Odors

Whistling sounds or musty odors coming from your vents indicate that your air ducts may have leaks in them.

How to Shut Off Your Furnace Manually

If your furnace refuses to turn off, your next step consists of turning off the furnace yourself and contacting a professional HVAC technician. Turn your thermostat off and switch from heating to cooling. This action should tell your furnace that you want it off completely instead of letting it try to continuously meet your temperature settings. 

Next, locate the power button on your furnace and turn that off. After the system powers down, contact a professional furnace repair company.

Professional Residential and Commercial Furnace Repair with JC Heating & Cooling in Hodgkins, IL

“Why is my furnace still running when turned off?” and “why does my furnace keep tripping the reset button?” are questions we gladly answer on our blog. If you need furnace repairs in Hodgkins, IL, call the HVAC pros at JC Heating & Cooling at (708) 968-3131.