Troubleshooting Your Furnace: Why It Keeps Turning On and Off

With over 50 years of unwavering dedication to providing top-notch HVAC services in Houston, TX, we understand the significance of a reliable furnace, especially when the Texas weather throws us a chilly surprise. If you’ve ever encountered the frustration of your furnace kicking on only to shut off moments later abruptly, you’re certainly not alone.

This perplexing issue can leave homeowners perplexed and yearning for solutions. But fear not! In this guide, we’ll delve into the potential reasons behind your furnace’s intermittent behavior and equip you with practical troubleshooting tips and tricks to try before seeking professional assistance. With our longstanding commitment to excellence, The Lee Thompson Co. is here to empower you to maintain a comfortable and cozy indoor environment. Let’s unravel the mystery behind your furnace’s on-and-off issue together!

A typical furnace will run three to eight heating cycles every hour; on average, these cycles will last 5 to 15 minutes. These cycles will vary depending on things like the temperature outside, the size of your home, the type of furnace, insulation, etc. If your furnace is turning on and turning back off after just a few minutes or starts more than eight times an hour, this is referred to as short cycling and is something you definitely don’t want to ignore. If left uncorrected, this will cause your furnace to struggle to heat your home, increase your energy bills, and put unnecessary stress on your system.

Let’s dive into the 11 common reasons your furnace is turning on and back off shortly after.

  1. The first common reason your furnace turns on and back off quickly is a lack of airflow that a dirty air filter can cause. When there is not adequate airflow through the system, the heat exchanger will frequently heat up and turn off when it has reached its maximum temperature, causing your furnace to turn off. If you haven’t recently changed your air filter, do a visual inspection and change if necessary. The air filter traps dirt, dust, and other debris and can block the airflow through your system if not routinely changed. Replacement every 90 days is the recommendation for a household free of allergies or pets and 60 days (or less) for households with pets or allergies.
  1. The next thing to check to ensure that your furnace doesn’t turn off for lack of airflow is your vents. You might have closed some of the vents in the past and forgotten to re-open them. You will also want to visually inspect the vents to ensure there are no foreign objects or debris blocking the airflow through the vents. It’s always best to keep all vents open to prevent any damage to your system from overheating. If you think there may be damage to your system, don’t hesitate to contact the experts at The Lee Thompson Co. – we’re always happy to help! Give us a call at (713)766-4846.
  1. A dirty blower wheel is another likely culprit for your furnace turning on and back off too quickly due to airflow issues. The blower wheel has blades that are designed to push the air from your furnace to the vents. If these blades become dirty, it won’t work as efficiently or sometimes at all. Routinely changing your air filters will ensure that dirt doesn’t build up on these blades. One of our licensed technicians would happily help you with this repair – Request Service.
  1. If your furnace is still turning on and quickly back off, your thermostat is the next place to check. A furnace turning on and back off too quickly can be a sign of a malfunctioning or broken thermostat. Several things can cause your thermostat not to work properly. If your thermostat needs new batteries, it will often malfunction. It’s also a good idea to do an inspection of the wiring to your thermostat to make sure they are not old and needs replacement. Lastly, a thermostat that has been placed too close to a heat source (like direct sunlight or a heat register) can skew the temperature reading and cause the thermostat to turn on and off irregularly. If you are concerned about old wiring or would like to relocate your thermostat, call The Lee Thompson Co at (713)766-4846, and we’ll send out an HVAC technician to get you taken care of.
  1. A dirty or broken flame sensor is the next likely culprit for your furnace’s short cycling. The flame sensor is in place to detect the flame and signal the gas valve to open. If there is no flame or if the sensor is malfunctioning, it is a safety feature that will turn off the gas valve to keep gas from leaking into the house. The system will shut down and restart when this gas valve turns off. You can access and try to clean off the flame sensor or call in the professionals at The Lee Thompson Co if you don’t feel comfortable or if you think the sensor needs replaced. Call us anytime at (713)766-4846. First, make sure you turn off the gas to the furnace and then remove the front panel where you will find the ignitor or ignition sensor near the burners. If the sensor or ignitor is dirty, you can remove it carefully with a screwdriver and gently clean it – be careful not to break it. Once cleaned, replace it back how you found it, put the front panel back on, turn on the gas, and then turn your furnace on.
  1. Another possible cause of your furnace turning on and off quickly is an issue with your furnace blower motor. The purpose of the furnace blower motor is to circulate the warm air throughout your house. It’s rare for the system to run still when the blower motor is off, but it can happen, and this would cause your furnace to short cycle. When the furnace is running, check to see if air is coming out of your vents. If there is no air or minimal air coming out of the vents, you likely have an issue with your furnace blower motor. Routine system maintenance can ensure that these parts of your furnace are properly maintained and will minimize issues such as this. We offer our Home Comfort Maintenance Plan for affordable twice-yearly maintenance to keep your system running efficiently – https://leethompsonac.com/home-comfort-plans/#/
  1. Another thing to check if your furnace is short cycling is your flue pipe, otherwise known as your exhaust vent, which can be found on your roof. Debris, such as dirt, sticks, leaves, or a bird nest, could be blocking the vent. If this becomes blocked, it will cause hot gases to build up in your furnace, causing it to overheat. Your furnace is equipped with another safety feature that will shut your furnace down if it is overheating. Checking to make sure there are no obstructions to your flue pipe routinely is a great way to avoid these potential issues.
  1. A faulty pressure switch is another common cause of your furnace turning on and back off after a few minutes. The pressure switch is in place to close with the airflow from the draft inducer motor through the burner to indicate that combustion is safe. If your switch is defective, it will not let the system know that ignition is safe to continue. If this happens, the ignition will be paused after just a few minutes, and the furnace will then turn off. If you have a multimeter, it can help you determine if there is an issue with your pressure switch.
  1. Like the pressure switch, the inducer motor is another part of your furnace that can become faulty and cause your furnace to turn off after just a few minutes. The draft inducer motor draws air into the burner and pushes it out the flue, as well as bringing in enough air to allow the pressure switch to close and activate the ignition process. If this part becomes defective, it won’t let the pressure switch close to ignite the furnace, and it will ultimately shut the furnace off after a few minutes.
  1. Believe it or not, you can have too big of a unit for the size of your home, which can cause your furnace to short cycle. When the unit is too big for your house, it will heat your house too quickly and then turn off abruptly. When your home becomes cool again, the cycle will repeat. In this instance, the only resolution to this problem is to replace the unit with one that is appropriately sized for your home. If you need a new, properly sized system, call the experts at The Lee Thompson Co at (713)766-4846. We take the time to ask questions about your needs and are expertly trained to ensure we help you select the best unit for you. We offer a variety of financing options and can find a payment plan that works for your budget – https://leethompsonac.com/financing/#/
  1. There are a handful of other reasons that will require professional assistance that may be causing your furnace to turn back off just minutes after it’s turned on. Our HVAC technicians undergo continuous training to diagnose and quickly fix any issue that may arise with your furnace, so call us today to get you back up and running – (713)766-4846!
    • Control board failure
    • Overheating heat exchanger
    • Damaged fan limit switch
    • Rust or corrosion to the system due to water damage

As we conclude, we trust that this blog has shed light on troubleshooting the perplexing on-and-off behavior of your furnace. With over 50 years of dedicated service in the Houston area, The Lee Thompson Co. remains steadfast in our commitment to providing unparalleled HVAC solutions.

Whether you’re grappling with Texas’s unpredictable weather or simply seeking reliable comfort in your home, we’re here for you every step of the way. If you’ve attempted the troubleshooting tips outlined in this blog and find yourself still in need of assistance, don’t hesitate to reach out to our seasoned professionals at (713)766-4846. Your satisfaction and comfort are paramount to us. Thank you for entrusting The Lee Thompson Co. as your premier HVAC partner. Stay warm and cozy and know we’re always here to ensure your indoor comfort.

Posted in Uncategorized