Why Isn't Your Furnace Turning Off?

Front view of falling snow with home during rare storm in Pacific Northwest of United States

On a cold day, it can be comforting to hear your furnace kick on to warm your home. However, when you have a heating system not shutting off when it should, you may wonder about problems like excess energy consumption and the strain on your heating unit. When the heating temperature becomes too high, and your furnace doesn’t turn off, even after you adjust the thermostat, it could even overheat the system and damage individual components.

Fortunately, a quick call to our team here at Thomas & Galbraith Heating, Cooling & Plumbing can help. We are available to come out to your home anytime day or night to see what’s going on with your furnace, and we can fix most minor issues on the spot to make your home more comfortable. Our NATE-certified team specializes in taking care of issues plaguing your furnace, so your space can stay at your ideal desired temperature.

Why Heaters Don’t Turn Off Properly Sometimes

Furnaces and their corresponding thermostats are designed to turn off when the desired temperature in the room has been reached. However, when this normal process doesn’t occur, these issues could be present.

1. Incorrect Thermostat Settings

When your thermostat doesn’t turn off when it should, check your thermostat first. Oftentimes, HVAC systems can be turned up by other members of your household without your knowledge, or the system may not be programmed properly. Anytime the temperature setting is far above the current temperature, your furnace will run as much as possible to warm up the room. Here are a few things to check when you inspect your thermostat.

  1. Room Temperature: Check the thermostat setting to see what it is set at. Make sure the unit isn’t set too high and adjust the temperature down according to your preferences.
  2. Furnace Response: If the setting is correct, try to turn off the furnace by manually lowering the desired temperature. If your furnace turns off, your unit may have been simply set too high. If this doesn’t trigger the blower to stop, turn your unit to “OFF” from heat to see if that helps.

2. Improper Fan Settings

Your furnace blower motor is designed to work in tandem with your air conditioning and furnace but may also work independent of your unit. Sometimes, people use the fan to circulate air throughout their home, which can be helpful after having carpet cleaned or when you are trying to filter your indoor air. However, it is important to check your thermostat to make sure the blower fan unit isn’t set to run continuously, since this can drive up energy consumption. Here are a few things to check.

  1. On your thermostat, look for the fan settings. There should be two, “ON” and “AUTO.”
  2. If it seems like your furnace won’t turn off, the thermostat may be set to “ON” for the blower. Toggle the switch to “AUTO” so your furnace’s blower fan only runs during a heat cycle. If “ON” is left on, your blower motor will run continuously, which can make it seem as if your air conditioner or furnace is generating and distributing cold air, since the unit will blow, even when a heat cycle isn’t in effect.

3. Dusty Air Filter

Since forced air furnaces and heat pumps with an air handler move air through your home, they use filters to remove dust and dirt. When filters become dirty, air movement is limited, which can cause your furnace to work harder than it needs to. Fortunately, by replacing your air filter, you can prevent problems. Here are a few steps for replacing your air filter.

  1. Open the access panel and remove the old filter from the compartment. Remove the old filter from the filter compartment.
  2. Insert a new filter of the same dimensions into the filter compartment. Make sure the filter is positioned correctly according to the arrows on its frame.
  3. Dispose of the dirty filter and replace the filter compartment’s access panel, if applicable.

* If your system uses a washable filter, lay the filter flat with the dirty side up and use a vacuum to remove debris. Rinse the filter with water to remove any leftover particles. Allow the filter to fully dry before reinserting it into the unit.

4. Thermostat Problems

Thermostats constantly track the air temperature inside your home and respond appropriately to turn on or off the heating. Unfortunately, if there are issues with your thermostat, such as loose wiring, the unit may not operate properly. Here are instructions for checking and tightening thermostat wiring.

  1. Switch off the power to your HVAC system by using the circuit breaker.
  2. Take off the thermostat cover to access the internal wiring.
  3. Look for loose wires. Some wires may have connections that aren’t seated properly, or that may have been pinched. Uncrimp wires by pushing them out of the way and tighten wiring connections with a flathead screwdriver.
  4. Replace the cover to the thermostat and turn the power back on.

If tightening wiring doesn’t fix the problem, you may benefit from a replacement thermostat. Sometimes, sensors or delicate components inside the thermostat can go bad, and the most inexpensive way to resolve the problem is a full replacement. Many new thermostats offer features homeowners find helpful, and may even improve energy efficiency.

When to Schedule Repairs

If your furnace continues to run, regardless of any troubleshooting you try, give us a call. Here at Thomas & Galbraith Heating, Cooling & Plumbing, we can check for problems such as faulty limit switches, compressor contact, or malfunctioning blower units and fix the problem to protect your furnace. Give us a call if you need a little help with your system.

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