Why Does My Furnace Keep Turning Off?

Are you waking up in the middle of the night to the cold, or hearing your furnace cycle on and off frequently? Fortunately, you’re not alone. If not diagnosed and corrected immediately, your utility bills may skyrocket or you may begin repairing your furnace frequently, leading to a replacement altogether. When your unit is frequently turning on and off, it’s called short cycling. Our team CARES about your comfort so we listed some of the most common causes of why this might be happening below. 

Low Airflow 

If your furnace is continually shutting off, it could be due to low airflow. There are several factors that can cause low airflow. 

• Dirty Air Filters: Regularly changing your system’s air filters is crucial to the integrity of your unit and its performance. Failing to do so can result in clogged, dirty air filters allowing the heat exchanger to retain heat and eventually overheat. Always change your air filters every 30 to 90 days and even more frequently if you have pets or allergies. 
• Dirty Blower Wheel: If your system is cycling on and off quickly, it could be due to a dirty blower wheel. The blower wheel has blades that circulate air. If the blades have debris on them, their performance will not be as efficient. You can prevent this by regularly changing your filters, but if you don’t, you may face an expensive repair. 
• Closed or Blocked Air Supply Vents: Another cause for a furnace frequently shutting off is blocked air vents. Simply check if air vents are closed or blocked in any way. You should always keep your vents open, even in the rooms you don’t use. If your heat exchanger doesn’t get enough air, it can’t transfer enough heat and the heat will build up, causing your furnace to short cycle.

Faulty Thermostat

Your home’s thermostat is what controls your entire heating and cooling system. So, if your furnace continually shuts on and off too quickly, your thermostat may be malfunctioning or broken. If the wiring is old, the unit could require new batteries or the location of the thermostat itself may need to be changed. If your thermostat is located near a heat source, such as direct sunlight or a heat register, it may skew the reading temperature, causing your unit to turn on and off. Unless your thermostat just needs new batteries, you should give a trained professional a call to rewire or relocate your thermostat. This is not something you want to attempt a DIY fix on! 

Flame Sensor 

Your furnace’s flame sensor lets it know when the gas valve is open. So, if your system is shutting off too often, it could have a corroded or dirty flame sensor. If there is no flame, the sensor will shut off the gas valve to keep the gas from getting into your home. If the flame sensor is dirty or has become corroded, the flame won’t register and will ultimately turn off the gas valve, resulting in your furnace shutting down. You will need to contact an HVAC professional to inspect and mitigate the issue, as it should only be handled by a professional. 

We hope this has helped guide you through a furnace that frequently turns on and off. A home with a functioning furnace is a HEALTHY HOME! Our team is dedicated to providing the greater Monoroe area comfort through our heating and cooling services. Give our team a call if your system continues to short cycle (704) 243-8081.