Why Is My Furnace Blowing Cold Air?
Expecting heat but getting the cold shoulder from your furnace? You’re in the right place!
A furnace blowing cold air can be pretty stressful. Read on for some information about how your furnace works and why it might be blowing cold air. A few of the common culprits can be fixed yourself, but others may require a little intervention from the professionals.
How Your Furnace Works
While a furnace may seem like a complicated system, it is actually quite simple to wrap your head around once you learn how it works. Gas furnaces bring natural gas (most commonly, but sometimes other fuel sources) into a combustion chamber, which is then ignited either via electricity or an always-burning pilot light.
The combustion process heats up the furnace’s heat exchanger (a series of coils or pipes). The furnace then uses a blower fan to push room temperature air through the system. This air absorbs heat as it passes through the heat exchanger’s coils before it’s pushed out into your ducts.
The hot air spreads throughout your home, giving it that warm, cozy atmosphere perfect for cold winter days. Any dangerous gas byproducts like carbon monoxide—collectively called combustion exhaust gas or flue gas—are vented safely outside of your home.
Reasons a Furnace Might be Blowing Cold Air
Okay…that’s all great, but why is my furnace blowing cold air?? Great question and one that has a few answers. Furnaces may blow cold air for a number of reasons. Some of these issues are easy DIYs but some may require professional help.
The Thermostat Is Set Incorrectly: Seem obvious…but the first thing to do when your furnace is blowing cold air is to make sure your thermostat is set correctly. When switching over from AC use in the late summer to turning on your heat in the fall or winter, it is easy to forget to adjust all the necessary settings. Make sure your thermostat is set to “heat” and not “cool” and set the fan to “auto” as opposed to “on.” If your system’s fan is set to “on” it will blow air all the time—even when the furnace is not producing hot air.
Bad Thermostat: It’s pretty uncommon for a thermostat to break (especially if it was successfully used to control AC during the summer months) but it can happen. Thermostats tell your HVAC system to turn on heat by sending a message to the furnace’s control board. It is possible that your thermostat is only telling the fan of your furnace and not turning on the burner to create hot air. If there was an issue with the thermostat or furnace installation or your thermostat is an older model, this may be the cause of your cold air.
Furnace Needs More Time to Heat Up: If this is the first time during the year that you’re turning on your furnace, you may just need to give the system more time to heat up. Much like turning on a shower, the system can take some time to fully heat up. If after 10 to 15 minutes your air still feels cold, a different issue is more likely.
Pilot Light Is Out: If your home furnace is 20 or more years old, it’s more likely to have a pilot light that burns continuously so that the larger burner can ignite whenever needed. Relighting a pilot light is a relatively easy and straightforward process for most homeowners, and often the instructions are printed right on to the side of the appliance. If the light continues to go out after relighting, give us a call and we can work out any other issues in the system.
Gas Supply Is Off or Weak: Like most Utah homeowners, if you have a gas furnace, it may not be receiving a steady supply of gas to the heat-generating burners. If your gas supply is off or simply insufficient, the furnace will be unable to generate heat but may still run the blower, thus producing cold air. If you have a gas furnace, you likely have a gas oven or range as well, so you can troubleshoot whether it is a gas supply issue to your whole home or just to the furnace. You’ll have to check with your gas company if it is a whole-home issue or call a professional like CTR if only the furnace is not getting enough gas.
Leaky or Damaged Air Ducts: Your furnace sends (usually) hot air through your home using a system of ducts that travel through your walls. If you can determine that your furnace is producing hot air, but the vents do not seem to be emitting it into your house, the ducts may have a major leak that is allowing air to escape. Damaged ductwork would also cause an issue with your AC, so it is important to get the system repaired as soon as possible. Finding holes or cracks in your ducts and sealing them should probably be left to a professional, as they have tools designed to assist in that process.
Dirty or Clogged Air Filter: Another common issue that could result in your furnace blowing cold air is a clogged or dirty air filter. If your furnace won’t blow air across the heat exchange coils, the system will likely overheat and shut down, resulting in just cold air. The filter is easy for a handy homeowner to remove and clean—or replace, if necessary. You can find affordable air filters right here on our site. We have filters for nearly every system at the very best prices…all with free shipping right to your home. If you need help swapping or upgrading your filter, we can certainly help with that as well.
Overheated System: A huge number of other technical reasons may cause your furnace to overheat—any of which could lead to a shutdown. Whether it is a clogged or dirty filter, a mechanical failure or even just wear-and-tear from old age, furnaces easily overheat and shut down. The shutdown is a good thing since it stops your furnace from catching fire, releasing carbon monoxide or even exploding. If you suspect your system is overheating, please give us a call right away so we can come troubleshoot the situation.
Routine Maintenance Can Help
Like any other complex system, your home’s HVAC system needs love and attention from time-to-time to keep it working at its best. Here are some things your can do to ensure your system performs in tip-top condition.
In addition to replacing your filter regularly, we also recommend an annual tune-up and inspection. Our $69 tune-up and inspection is designed to keep your healthy system running its healthiest. Our tune-up and inspection service includes a full suite of services and is an excellent way to ensure peak performance from your healthy HVAC system. To schedule your tune-up, give us a call at 801-999-4220 or use our convenient online scheduling. We look forward to taking care of you now…and for many years to come!
