Why Is My Furnace Running Constantly?

December 22, 2016

Wondering what’s causing your furnace to run constantly? Well, that depends on whether or not your furnace is heating your home to the set temperature. That said, there are two possible scenarios at play here:

1. Your furnace runs continuously but never heats your home to the set temperature. This problem is caused by these furnace issues:

  • You’re setting your temperature too high and the furnace can’t keep up
  • Your furnace is suffocating (usually due to a clogged filter)
  • You have leaky air ducts

2. Your furnace heats your home to your set temperature and then continues to run non-stop. This means you most likely have a problem with your thermostat or thermostat wiring.

First, determine which of the above describes your problem. Then skip to that section below. We’ll explain what you need to do to fix the problem.

Need a professional’s help? Just contact us and we’ll send a tech out immediately.

1. If your furnace runs constantly but never heats your home to your set temperature…

...there are 3 possible issues that could be causing this problem. Read on for an explanation of those problems and what you can do on your own to fix the problem before calling a pro.

Possible problem #1: You’re setting your temperature too high

Check your thermostat’s temperature. In Missouri, the average winter lows hover around the 20s so if your thermostat is set super high (say 85 or higher), your furnace may struggle to keep your home warm and run constantly to try and keep up. 

What to do: First, try adjusting the thermostat to a temperature that’s lower than the current indoor temperature. If the furnace stops running after 3 to 4 minutes, it means your set temperature is too high. Adjust your thermostat anywhere from 68 to 72 degrees to avoid this problem in the future.

Possible problem #2: Your furnace is suffocating

Your furnace can only put out as much air as it “breathes” in. So, if it isn’t getting enough airflow, it can only put out a limited amount of hot air. And that means it will run constantly, trying unsuccessfully to heat your home.

What to do: Check and change your air filter if it looks like the filter to the right below. A clogged filter restricts the amount of air your furnace can breathe in. 

A clean filter (left) vs a clogged filter (right).

Also, make sure all return air vents (the vents that “breathe” in cold air from your home) are unobstructed. Move any drapes, furniture or plants that might be preventing the vents from accessing enough air.

If your furnace continues to run after you’ve done both of these things, have a professional inspect your system.

Possible problem #3: You have leaky air ducts

If your ducts are leaky, it means hot air is escaping into unconditioned areas instead of blowing into your home. And with enough hot air escaping, your furnace will run constantly without ever reaching your set temperature.

Screen Shot 2016 12 22 At 1 45 16 Pm

What to do:  Have a professional inspect your ductwork for leaks. They’ll be able to verify if this is your problem and seal leaky areas.

2. If your furnace heats your home to your set temperature and then continues to run non-stop…

...you most likely have a problem with your thermostat or thermostat wiring.

You see, your thermostat is responsible for communicating with the furnace and telling it when to turn on and off. So, if your furnace is successfully heating your home to the set temperature but then continues to put out heat, your furnace likely isn’t getting the “TURN OFF HEAT” signal from the thermostat.

What to do: Change the batteries in your thermostat just in case your batteries are getting weak. If your furnace continues to heat, though, you’ll need to have a professional inspect your thermostat for wiring issues. They’ll be able to repair or replace a bad thermostat.

Need help from a Kansas City tech?

If you’ve tried some of our DIY suggestions but your furnace is still running non-stop, we’re here to help.

Just contact us and we’ll send out an experienced tech to solve the problem!

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