It's the middle of winter, and you're expecting warm air to come out of your furnace. But instead, all you're getting is cold air. What gives? Why is your furnace blowing cold air rather than heat? In this blog post, we'll discuss a few potential causes of why your furnace might be blowing cold air.
Reasons Why Your Furnace May Be Blowing Cold Air
The Pilot Light Is Out
One possible reason your furnace is blowing cold air could be that the pilot light is out. If the pilot light goes out, the furnace won't be able to produce heat. Fortunately, relighting the pilot light is relatively easy and only takes a few minutes depending on the model you have. We recommend looking up the unit and model of your furnace for instructions on how to re-light your pilot light.
Professional tip: Use some tape and a marker to label any switches nearby so you are never left guessing again.
Disclaimer: If you have no experience working with an HVAC system, or are unsure about what you see in your furnace, please do not attempt to repair your system and call an HVAC professional instead.
Air Filter Is Dirty or Clogged
Maintaining a pristine air filter is essential for the optimal circulation of air in your system. A clogged or dirty filter can impede the delivery process and decrease efficiency, so it's important to make sure yours remains clean at all times.
To check if your air filter is clogged, gently slide it out from the furnace panel. If there’s dirt or dust buildup on either side of it, then go ahead and replace it right away with a new one that’s rated at least MERV 8 (the higher the MERV rating, the greater the filtration capabilities).
We recommend you inspect your filter every 1-2 months and replace it as needed for optimal performance of your furnace system throughout the year!
Professional Tip: Minimum Efficiency Reporting Values, or MERVs, report a filter's ability to capture larger particles between 0.3 and 10 microns (µm).
Thermostat Problems
Your furnace may not be creating any heat due to a thermostat problem. A common reason a furnace is not heating a home is because the settings and scheduled temperatures are incorrect. This may occur from an app if it is a smart thermostat, or if the thermostat has recently been reset. However, there may also be calibration issues with the thermostat itself that create a heat discrepancy in the home. To test your thermostat, try adjusting the temperature settings (e.g., 60°F vs 75°F). If nothing happens after doing so or you continue to feel cold air, then go ahead and try resetting/rebooting both systems by turning them off/on again at their respective main power sources (i.e., breaker box & wall outlet).
Your Furnace Has Overheated
If your furnace was running too hot, it will activate a protective mechanism that automatically shuts down the system. This means you will have no heat until the system restarts - the restarting process could take up to three hours depending on the model of the furnace.
There are a few reasons your furnace could be overheating (besides a clogged filter):
If your filter has been blocked, then dirt particles and debris may have found their way into other sections of your furnace too. If that debris is cluttering up moving parts such as the blower, it could easily lead to an overheated system.
With regular use, your furnace may start to overheat due to a mechanical breakdown. This could be the issue if you have an older furnace, as worn-out parts are more prone to malfunctioning and ceasing operation altogether. It’s best to get professional help from a certified HVAC technician to assess and repair your furnace or quote you on a replacement system.
Speaking of replacements, as time passes, unfortunately, your furnace will begin to decline in performance. Generally speaking, a well-cared-for furnace has an estimated lifespan of 15 years; however, certain components may become damaged and cause it to overheat before then. Commonly the burner itself or other elements such as the flame sensor are the first components to become damaged and in need of replacement.
The Air Ducts Are Leaking
If you have holes, disconnections, or leaks in your air ducts, then all the hot air is escaping before making it through your vents. Leaking ducts have more of an effect than you’d think, and duct sealing would fix this problem—either with tape or new pieces depending on the damage.
The Condensate Line is Clogged
If your furnace is not working properly, be sure to inspect and clean the condensate lines regularly. Clogs in these lines can result in an inability for your furnace to ignite; this will cause only cold air to come from your furnace. One sign that your condensate line is clogged is if you see water pooling under or near your HVAC unit where you do not typically see any. If you're still unsure of what's causing the issue, don't hesitate to call your greater Boston HVAC company, Home Mechanics and we will be able to assess and fix any problems with your furnace.
There’s A Problem With The Gas Supply
If your pilot light is going out instantly or not lighting at all, it may be an issue with the gas supply. If this is the case, we have good news: your furnace has safety features designed to shut off if it detects an issue with the gas supply. In either case, we recommend turning off the gas line and seeking professional advice.
There might be an inadequate gas supply in your tank, but it might also be an issue with the gas supply lines to your furnace. If your pilot light doesn’t light at all, it may also be the gas valve. This is not an issue that you can repair on your own. We recommend you call a licensed HVAC gas fitter in Massachusetts.
We Can Help Fix Your Furnace
If you are in need of a furnace repair, you can trust our furnace experts here at Home Mechanics. We are proud to service the greater Boston area. Check out our service areas, here, or give us a call at 978-539-7172.