How Do You Fix a Gas Furnace That Won’t Turn Off?

Repair technician fixing gas furnace

Ideally, your furnace should cycle on when the thermostat senses that it’s too cool in your home, then turn off when the temperature reaches the set point of the thermostat. If it’s not cycling on and off but running constantly instead, a few possible issues could cause this problem.

Why Is It Bad for Your Gas Furnace to Always Be On?

When your gas furnace runs all the time with no breaks, it will increase your energy bills substantially and could damage the furnace and shorten its life span.

Components like the blower motor or induction motor could overheat, damaging the motor windings and bearings, or the heat exchanger could overheat and crack. These are expensive repairs, so addressing the problem quickly is important to avoid further damage.

What To Do When Your Furnace Won’t Turn Off

Several issues can stop a furnace from cycling on and off properly. Here are some of the most common problems to check for and their possible solutions:

  • Incorrect temperature settings: Make sure your thermostat is set correctly. If the set temperature was raised inadvertently, the furnace will continue running until that temperature is reached. Change the thermostat to a lower setting than the current room temperature so the furnace turns off.
  • Wrong fan setting: Normally, the furnace’s fan should turn on shortly after the furnace does and shut off soon after the furnace turns off. If the fan is set to “On” instead of “Auto,” it will run constantly, even though the furnace is off. This can make it seem like the furnace is running. Set the fan back to “Auto” so it cycles normally.
  • Low thermostat batteries: If you have a digital or programmable thermostat, it’s typically powered by batteries, and if these are low or dead, the furnace may not cycle properly. Replace the batteries at least twice a year.
  • Faulty fan limiter: The fan limiter controls the cycling of the blower fan, delaying it slightly when the furnace turns on to avoid blowing cool air through your home and turning the burners off to protect the heat exchanger if the furnace gets too hot. If the fan limiter is faulty, it may allow the fan to run constantly. To fix the problem, have it replaced by a professional HVAC technician.
  • Dirty air filter: If your furnace filter is clogged with dust and debris, it can interfere with airflow through the ducts and the thermostat’s temperature readings, stopping the furnace from cycling properly. To fix the problem, improve your air quality and keep your furnace running as efficiently as possible, check the air filter every month and replace it as needed.
  • Leaking air ducts: If your furnace is running, but much of the hot air is escaping through leaks in the ductwork, the house may never reach the set temperature on the thermostat, and the furnace will keep running. Have a professional inspect and repair the ductwork.

Schedule Furnace Service With Andreas Plumbing, Heating & Air Conditioning

If your furnace won’t shut off, contact our home heating experts at Andreas Plumbing, Heating & Air Conditioning.

We offer in-depth diagnostic services and furnace repairs to quickly resolve any problems you may have with your furnace, and complete furnace maintenance that can prevent problems in the future while keeping your heating costs as low as possible and making your furnace last longer.

When you want to make sure your furnace is always performing at its best, our Service Partner Plan is a great value. It offers all your annual HVAC maintenance and excellent benefits like priority service, no emergency service fees, and a 10% discount on all HVAC services.

Our company serves homeowners throughout Carbon County, Lehigh County, and Monroe County, and select areas of Northampton and Schuylkill counties. We’re a fourth-generation, family-owned HVAC company offering top-rated customer service and quality that reflects our commitment to honesty, integrity, and hard work.

Call Team Andreas at (610) 377-5261 today to schedule furnace service in Carbon County.