Navigating the Chill: A Guide to Troubleshooting Your Furnace Blowing Cold Air

If you’ve found yourself here, chances are you’re experiencing the frustration of a chilly home despite your furnace being on. Don’t worry; you’re in good hands. Many residents in Golden, CO, and the surround areas encounter similar challenges, especially as winter sets in against the stunning backdrop of the Rockies.

Since 2002, Singletrack Electric & Heating has been Golden’s trusted source for expert electrical and HVAC services. With our dedication to excellence and commitment to customer satisfaction, we’ve earned a reputation as the go-to experts for all things heating and electrical in the area.

In this blog, we’re excited to share our knowledge and expertise to help you navigate the chill and restore warmth to your home. Whether you’re a seasoned DIY enthusiast or just seeking guidance before calling in the pros, we’re here to empower you with the tools and information you need to troubleshoot common heating issues.

So, grab a cup of hot cocoa, cozy up, and let’s embark on a journey to ensure your home stays warm and comfortable through the winter months. With Singletrack Electric & Heating by your side, you can trust that your heating needs are in capable hands. Let’s dive in and tackle those heating troubles together!


Here are the 9 most common reasons your furnace is blowing cold air.


  1. Thermostat Issues
    The first most common cause of your furnace blowing cold air is your thermostat. Since your thermostat controls your home’s temperature, incorrect configuration can lead to cold air coming through your vents. You’ll want to verify the settings and your thermostat to make sure that someone hasn’t changed them. You want to ensure the thermostat is set to ‘heat’ and not ‘cool, make sure the fan is set to ‘auto’, and make the temperature is set where you would like it. A furnace with dead or dying batteries, can also cause the thermostat to malfunction, so changing your batteries may be helpful as well. If any of these settings are incorrect, make the appropriate changes and your furnace should begin blowing warm air. Keep in mind it takes about 15 minutes for a furnace to heat up, so please be patient and allow it time to warm up.

  1. Dirty Air Filter
    If your furnace is still blowing cold air, the next place to check is your air filter. Your air filter traps dirt, dust, and debris within your system and if not changed routinely can lead to restricted airflow in your system. When the airflow is restricted, the cold air entering the furnace from the return ducts is limited and leads to your furnace not having sufficient air to heat. Further, a dirty air filter and cause your furnace to overheat and go into safety mode. Depending on household factors like pets and allergies, it’s recommended that your furnace filter be changed every 30 to 90 days. If it’s been a while, putting in a fresh air filter just might do the trick.

  1. High Limit Switch Issues
    If your furnace filter was dirty and replacing it didn’t help, the issue may be a faulty high limit switch. This switch measures the temperature of the air that passes over the heat exchanger within your system and shuts down the furnace if it overheats. Lack of airflow is a very typical cause of your furnace overheating. If you experience frequent tripping of the high limit switch, it can cause the switch to fail. If your blower continues to run between cycles or cycles on and off, this typically indicates a faulty limit switch. Give the professionals at Singletrack Electric & Heating a call at (303)215-9449; we’d be happy to get this issue taken care of for you.
  1. Fuel Issues
    A lack of fuel can be another common cause of a furnace blowing cold air. Based on your type of furnace, it runs on either electricity or fuel.
    1. If you have an electric furnace, it won’t function without electricity. You will want to ensure that the switch in your utility room that powers your furnace is in the ‘on’ position. You will also want to check at your breaker box and make sure that the breaker is in the ‘on’ position and has not tripped.
    2. If you have a gas furnace, it won’t heat up if the gas supply has been shut off, the gas valve has been turned off or has seized, or if the propane/oil tank is empty. You will want to check to make sure there are no issues with your gas supply and that the appropriate gas valve is open.

  1. Clogged Condensate Line
    Another common cause of your furnace blowing cold air is a clogged condensate line. Condensation from your furnace drains away via the condensate line, which is a white PVC pipe that runs down the furnace’s outside and empties into a floor drain. If the pipe becomes clogged, the condensation will accumulate in the drip pan and trigger the float switch. The float switch is a safety feature that shuts down the furnace when the condensation doesn’t properly drain to prevent water from spilling over the drip pan.

If you find a clogged condensate line is your issue, the clog must be cleared for your furnace to function properly. As a homeowner, you can try to take on this maintenance task, but the professionals at Singletrack have specialized tools to make the job easier and more efficient. Give us a call today at (303)215-9449.

    1. Before trying to clear the clog, you will want to make sure you turn off the power to your furnace. You can do this by flipping the switch (resembles a light switch) on the furnace or by turning off the breaker for your furnace at your circuit breaker.
    2. Inspect the end of the condensate white PVC pipe for debris. If you find any, they can be removed with a brush or a small screwdriver.
    3. If you didn’t find any clogs at the end of the pipe, you can remove the cap near the top of the pipe and flush the line with a solution of equal parts white vinegar and hot water. You can repeat this process several times if needed.
    4. Once you have cleared the clog, restore power to your furnace and give it time to warm up.
  1. Ductwork Issues
    Leaking or incorrectly sized ductwork can also lead to issues with your furnace blowing cold air. Call in the experts at Singletrack Electric & Heating to properly check and repair your ductwork to ensure optimal heating performance of your furnace.

    1. If your ductwork is leaking, it can cause warm air to leak out as well as allow cold air to enter through the openings in the ducts. Leaks are caused when ducts become disconnected or cracked.
    2. If your ductwork is incorrectly sized, it can cause issues with the heating performance of your system. If your return ductwork is too small, it won’t be able to handle the volume of air that’s needed to properly heat your home. This will need to reduced airflow through the system and will cause your furnace to blow cold air. Ductwork that is too big causes the air pressure to significantly decrease and therefore the airflow doesn’t make it to all the parts of your home.

  1. Flame Sensor Issues
    A dirty or malfunctioning flame sensor can be another common cause for your furnace blowing cold air. The flame sensor is a safety device that will turn off the gas supply to the burners in your furnace if they don’t ignite. These sensors can become coated with dirt, soot, or other carbon deposits and make them incapable of sensing the flame.

You can access and try to clean off the flame sensor or call in the professionals at Singletrack if you don’t feel comfortable or if you think the sensor needs replaced. Call us anytime at (303)215-9449.

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. Electric Ignition / Pilot Light Issues
    A faulty electric ignition or an issue with your pilot light can also cause your furnace to blow cold air. If your furnace was manufactured prior to 2010, they generally were still using pilot lights. More modern furnaces will use an electronic ignition.

    1. If your furnace has a pilot light, check to see if the flame has been blown out by a strong draft. If the flame has blown out, you will want to consult your furnace’s manual for instructions on re-lighting the pilot light. If the flame continues to go out, there may be dust or debris built up on the pilot light causing a bad connection.
    2. If you have a more modern furnace with an electric ignition, these electronic ignitions can fail and would require a call to the professionals at Singletrack Electric & Heating at (303)215-9449.

AC installation at denver home

  1. Incorrectly Sized Furnace
    Another common cause of a furnace blowing cold air is an incorrectly sized furnace for the home. Size matters when it comes to your furnace system. If you’ve recently installed a new furnace and find yourself puzzled by its failure to product hot air, chances are it’s undersized for your home. An improperly sized furnace can result in the circulation of cold air and can lead to issues with both effectiveness and efficiency.

    When your furnace is too small for your home, it struggles to accurately gauge the internal temperature, often resulting in the distribution of cool air. Conversely, an oversized furnace may cycle on and off unexpectedly, causing disruption to your comfort and potentially leading to higher energy bills.

    Our HVAC professionals are expertly trained to help your select the right size furnace for your house and your individual comfort needs. You can request an appointment anytime by giving us a call at (303)215-9449.

There are a handful of more serious issues that could be causing your furnace to blow cold air and would require a call to the professionals at Singletrack. Our technicians are expertly trained to diagnose and resolve these issues and have you back up and running quickly! Call now at (303)215-9449!

  • Malfunctioning Gas Valves
  • Cracked Heat Exchanger
  • Blocked Burner
  • Clogged Coil
  • Faulty Circuit Control Board

Opting for professional furnace maintenance with our Peak Membership Plan through Singletrack Electric & Heating is a proactive step towards safeguarded your home comfort. Our skilled technicians offer a comprehensive inspection of your heating system, proactively identifying potential issues before they lead to your furnace blowing cold air. By addressing these concerns, our team not only boosts your furnace’s efficiency but also guarantees its safe and dependable performance.

Our trained experts can pinpoint and resolve underlying issues that might escape the untrained eye, preventing unforeseen breakdowns and sparing you from expensive repairs down the line. With Singletrack’s Peak Membership Plan, you can rest assured that your furnace is in optimal condition, ready to keep you warm and cozy all season long. Give us a call to learn more here at (303)215-9449.


As we conclude this comprehensive guide to troubleshooting your furnace blowing cold air, we hope you’ve found the insights and tips helpful in addressing any heating challenges you may be facing. Remember, maintaining your heating system is crucial to ensuring its efficiency and reliability, and a little troubleshooting can often make a big difference.

However, if you’ve exhausted all the suggestions provided and your furnace is still blowing cold air, don’t hesitate to reach out to the trusted professionals at Singletrack Electric & Heating. With nearly two decades of dedicated service to the Golden community and our commitment to excellence, you can trust us to provide reliable and efficient solutions to your electrical and HVAC needs.

Your comfort and satisfaction are our top priorities, and we’re committed to keeping your home warm and cozy through every season. Whether it’s electrical repairs, HVAC maintenance, or a system upgrade, you can count on Singletrack Electric & Heating to deliver exceptional service every time.

Thank you for joining us on this journey to ensure your home stays warm and comfortable. Remember, Singletrack Electric & Heating is here for all your electrical and HVAC needs, ensuring that you stay comfortable no matter the weather outside! Stay warm, Golden!

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