Why Won’t My Furnace Shut Off?

Girl feeling in a bad mood and drinking hot drink

When your furnace won’t shut off, it feels like your heating equipment has a mind of its own.

Not to worry. At Doornbos Heating & Air Conditioning, we receive this common repair call whenever winter rolls around in Illinois. Fortunately for our Orland Park customers, it’s usually a simple fix.

However, if you’ve had your furnace for 15 years or longer, we recommend upgrading. Besides saving on frequent repair calls, you’ll reduce your energy consumption.

Upgrading your older gas furnace from 56 percent to 90 percent efficiency will save 1.5 tons of carbon dioxide emissions yearly, according to the U.S. Department of Energy (DOE). That’s a huge boost to the environment and the perfect way to reduce your carbon footprint.

Why Isn’t My Furnace Shutting Off?

Several factors could be making your furnace run nonstop. Sometimes, the solution is quick and easy. In other cases, it could require a more complex repair. Either way, our team of certified heating, ventilation, and air conditioning (HVAC) professionals is located nearby in Orland Park. Call us with any questions.

Here’s what could be happening:

1. Your thermostat has the wrong setting.

Rule this one out before calling in a repair. If your thermostat is set to on, change the setting to auto. Doing so ensures the fans will only blow air when your furnace is actively heating. Leaving the thermostat set to on tells your furnace fans to run nonstop.

Your thermostat could also be set too high—try lowering it a few degrees. An excessive temperature setting creates rapid heat cycles and might make your furnace seem like it’s always running.

2. Your thermostat is broken.

If the settings look normal on your thermostat, but your furnace won’t shut off, the thermostat itself may be faulty. It could be misplaced, misconfigured, poorly wired, or simply old and in need of replacement. Whatever the case, a Doornbos Heating & Air Conditioning professional can get to the bottom of it.

3. You need to replace your air filter.

A clogged air filter creates airflow issues that can make your furnace run longer to heat your Illinois home. You should change your filter at least every 90 days. Doing so makes your furnace run more efficiently, preserves indoor air quality (IAQ), and prevents costly repairs.

4. Your ducts are leaking.

Leaks and tears in your ductwork allow air to escape. Faulty air ducts can make your furnace run constantly because your home never gets warm enough to reach the thermostat temperature. Luckily, an HVAC expert can pinpoint any duct leaks using thermal technology. From there, your professional will perform duct sealing to restore proper air containment.

5. The furnace fan limit switch is broken.

The fan limit switch is supposed to trigger whenever you adjust the thermostat. It’s the part of your furnace that tells the blowers and heat exchanger to start cycling. When the limit switch isn’t working, it can make your furnace run ceaselessly. A team member from Doornbos Heating & Air Conditioning can quickly diagnose and repair this issue.