Welcome to the Indoor Comfort Team blog, your trusted source for HVAC and solutions in St. Louis, MO!

If you’re here, changes are you’re struggling with a furnace that won’t turn on. Don’t worry; we understand that importance of a properly functioning furnace, especially during the cold winters in St. Louis.


In this complete guide, we’ll explore 11 things that could be behind your furnace not turning on and provide helpful steps to resolve the issue.

Whether you’re a seasoned DIYer or prefer leaving it to the HVAC experts in St. Louis, our goal is to help you get your home comfortable again quickly and efficiently.

Join us as we navigate through troubleshooting tips and expert advice. Let’s ensure your home remains warm and cozy, courtesy of the Indoor Comfort Team’s expertise and dedication to your comfort for 45+ years.

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  1. If you have a furnace that won’t turn on, the first place to check is the furnace switch. This switch is your unit’s power source and is usually located on the side of the furnace or next to it and it looks a lot like a light switch. Verify that the switch is in the ‘on’ position. If the switch is flipped to the ‘off’ position, switch it to the ‘on’ position and see if your system starts up.

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  1. If this doesn’t get your furnace back on, your circuit breaker is the next logical place to check. The problem could stem from a blown furnace fuse or a tripped breaker. A tripped breaker will cut electricity to your unit, making it unable to turn on. If you find that the breaker is tripped, flip the breaker to restore power to your furnace, and your furnace should turn on.
  1. Another common cause of a furnace not turning on may be an incorrectly programmed thermostat, a malfunctioning thermostat, or a thermostat with dead batteries. Your thermostat is an essential part of your system and keeps your house at the exact temperature you want. Verify that the thermostat is set to ‘Heat’, at the correct temperature, and that it’s not set to ‘fan only’. Also make sure the batteries aren’t dead and that everything is functioning properly.


  1. Another thing to double-check is the thermostat wires. If these wires become broken or loose, this severs the communication with your furnace. By removing the thermostat, you can do a visual check to ensure the wires are securely attached, and there is no visible damage. If you don’t feel comfortable assessing or repairing the wires, one of the Indoor Comfort Team’s HVAC professionals is always willing to help. Give us a call anytime at (314)230-9542.
  1. If your furnace still won’t turn on, your next stop is to check out your air filter. If it’s been a while since the filter was changed, your airflow circulation may have become blocked. When airflow is blocked, it will keep your HVAC system from functioning properly. When the system does not have proper airflow, it will struggle to keep up, and there is a risk of overheating. To keep this from happening, it is recommended that filters are changed every 90 days for average households without pets.


  2. If you’ve tried all these things and your furnace still isn’t turning on, you will want to ensure that your gas valve shut off on the furnace’s gas line is turned on. If the handle is parallel to the gas line, you know it’s on. If the handle is perpendicular, however, this means the gas is turned off. You will want to rotate the handle until it is parallel to the gas line.


  1. While you’re in front of the furnace, check to make sure none of the access panels are ajar. Your furnace has many fail-sales placed in its design to protect homeowners. One of these safety features will turn off your furnace if any of the access panels are out of place. Do a visual inspection to make sure no panels are missing screws, out of place, or have been damaged in any way.


  1. One of the most common issues when your furnace is not turning on is a dirty or faulty ignition sensor. If you hear your furnace click on but not start running, this is likely your problem. This is something you can check yourself if you feel comfortable, or you can all on the experts at Standard Plumbing Heating and Air Conditioning to take a look at. First, 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, remove it carefully with a screwdriver and gently clean it – be careful not to break it. Once cleaned, replace it how you found it, put the front panel back on, turn on the gas, and then turn your furnace on. Adjust the temperature on your thermostat and see if your furnace starts up. Remember it may take a few minutes to start running, so be patient. If you’d rather have one of our experts take a look, contact us today – https://www.indoorcomfortteam.com/schedule-appointment/

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  1. Another thing you can check if your furnace isn’t turning on is your drain pan. This condensation drain pan is located under your furnace and is meant to collect excess water. If this pan becomes full, it will trigger the Safety Float Switch to shut down the whole system. Emptying and replacing the pan is a great short-term solution; you’re likely dealing with a clogged condensate line, drain, or a faulty pump. One of the experts at Standard can diagnose and solve this problem for you.


  1. The Indoor Comfort Team crew undergoes continuous training to ensure they are always ready to answer the call when issues arise. Various other issues within the system can cause your furnace to not turn on.
    • A bad capacitor
    • A dirty blower motor
    • A tripped High Limit switch
    • A triggered pressure switch

A call to the professionals at the Indoor Comfort Team will be needed to fix these things properly. We’d be happy to get you taken care of at (314)230-9542.

  1. Last, but definitely not least, it may be time to replace your aging system. Indoor Comfort Team can get you into a new Trane system for just $69 a month. Count on the team that has been the HVAC Experts in St. Louis for over 45 years – https://www.indoorcomfortteam.com/about-us/

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As we wrap up, it’s crucial to prioritize the maintenance of your furnace to ensure uninterrupted comfort during the chilly winters in St. Louis. If you’ve tried our tips and your furnace still won’t turn on, don’t hesitate to reach out to the experts of the Indoor Comfort Team at (314)230-9542. Our dedicated team is here to help you stay warm and comfortable all season long. Say goodbye to shivers – let’s get your furnace running again and keep you comfortable all season long!

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Contact us today!

Indoor Comfort Team has been a trusted name in the greater St. Louis area since 1979. Whether you live on the Missouri side of the river or in Illinois, our skilled and licensed HVAC technicians are ready to deliver the services you need.

We provide complete heating and cooling installation and repair as well as water heater and indoor air quality services.

Need a repair today? Call (314) 230-9542 or (618) 688-0707.

Whether you need repair, maintenance, or new installation of your furnace or air conditioner, contact us today to let us get our comfort specialists right to work on your home or business.

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