Why Is My Furnace Blowing Cold Air?

 In Furnaces, Home Maintenance

When it comes to staying warm in Southern Ontario during the winter, there’s nothing homeowners depend on more than their furnace. Even if you have regular furnace maintenance every year, it’s possible that older units may experience some issues throughout the season. If you find your furnace is blowing cold air this winter, find out what might be the cause.

1. Your Fan Setting Is Set to “On”

Your furnace has a fan component, which is responsible for moving all of that nice, warm air from inside the unit to the rest of your house. While it may seem like “On” would be the appropriate setting, it’s a mistake many homeowners make. Having your fan on this setting means that it’s on all of the time, even when your furnace has cycled off. While it blows hot air while your furnace is running, it will continue to blow cold air when the cycle is off. Make sure you check your fan’s setting on your thermostat and change it to “Automatic” before you call your furnace technician to solve at the problem.

2. Your Furnace Has Overheated

If you’ve checked that your thermostat is on the automatic setting, it’s possible that your furnace has overheated. This is the likely cause if your furnace has been on and blowing warm air, then cold air, and then has stopped blowing any air at all. Your furnace has a safety device called the limit switch which turns the burners off if it overheats. Air continues to blow so that the furnace can cool down to a safe level. You’re likely to experience an overheated furnace if you don’t clean or replace your filters, which can block airflow and cause the furnace to work harder. Try changing out your filters to see if that fixes the problem, and call your service technician if it’s still not working properly.

3. The Pilot Light Is Out

If your furnace runs on gas, it has a pilot light. A pilot light is a small flame that is always on, and it’s the ignition source for the rest of your furnace. You can tell if your pilot light is out in several ways. First, try relighting your furnace pilot light by following the instructions on your furnace. If it stays on, your furnace should be fine. If it doesn’t light, it may require some cleaning to allow gas to come through, or there may not be any gas flowing into your furnace. Check that your gas valve is in the “on” position. If your pilot light won’t stay lit, your thermocouple may need to be replaced. This is an easy fix for your furnace technician!

If your furnace stops working in the middle of the winter, you want to get it back up and running as soon as possible. No matter what the time of day, contact Bryan’s Fuel for 24/7 emergency service.


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  • Kathy allen

    Those are good tips and well worth knowing. Thanks

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