Why Does My Furnace Fan Keep Running?

It can get pretty irritating when your furnace won’t turn off, right? This means something is going on that could affect your utility bill and cost you money. There are a few reasons why your furnace keeps running, so following the process of elimination is key. In some cases, it’s a very easy fix because your fan limit switch is incorrectly set. What’s a fan limit switch?

The fan limit switch is what controls the thermostat. It turns the furnace on and off as needed. You can find it inside the panel cover near the upper right corner, or directly on the keypad if your thermostat is digital. You’ll know if it’s working correctly because the fan will turn on when heat is needed, and automatically turn off when the temperature is at the correct level.

On average, typical run times are between ten and fifteen minutes with about two or three cycles per hour. In extreme cold weather, the cycle time may be a little longer.

If you’ve found that your run cycles are off, here are a few suggestions on what to do:

• Check your fan limit switch
  This should be the first place to start. The switch should be set to AUTO and not ON. When it’s set to ON, it will keep running without shutting off. If you have a situation where it’s correctly set and the furnace keeps running after temp reached, it’s time to seek assistance.

• Listen to the fan
  If your Honeywell thermostat fan won’t turn off, the limit switch may need to be replaced. If you have set the fan to AUTO and it doesn’t stop running, professional assistance is needed. Although replacing the switch may be the cause, you may also have bad wiring to the thermostat. If the furnace keeps running thermostat off occurs, the problem will have to be evaluated and repaired by a professional.

HVAC systems can be tricky. Something that seems so minor could end up being something that costs time and money if not immediately taken care of. Let’s recap:

• Make sure the fan limit switch is set to AUTO
• Make sure the fan won’t turn off even when set to auto
• Make sure the fan won’t turn off even when set to OFF

If your issue is one of the three, don’t hesitate to contact an HVAC specialist to handle the problem. Make sure you’re changing the filters on a regular basis because this can also overwhelm the system and cause the furnace to constantly run. Additionally, if you have the temperature set too high, this could cause the furnace to run a lot to reach that temperature.

A faulty thermostat could keep the system running when it doesn’t need to, putting additional strain on the system. This not only creates problems for your system, but you’ll end up paying a lot more in energy costs when you shouldn’t have to.

For more information, contact an HVAC specialist to get your problem taken care of as soon as you detect a problem.