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7 Reasons Your Furnace is Blowing Cold Air & How to Fix

7 Reasons Your Furnace is Blowing Cold Air & How to FixA functioning furnace is a must when it comes to colder nights—there’s nothing like snuggling up in a warm house on a chilly evening. But what if your furnace starts blowing cold air right when you need the heat the most? There are seven types of problems that can cause your furnace not to distribute hot air. From dirty air filters to a malfunctioning thermostat, the reasons range from being a quick fix to something more serious.

Why Is My Furnace Not Blowing Hot Air?

It is important to know what to do and what to look for if your heater is not blowing hot air. Although not every single reason is listed, here are seven common reasons and solutions to a furnace blowing cold air.

1.) Contaminated Air Filter

One of the easiest problems to fix, a contaminated air filter may be the reason your furnace is not functioning properly. When a filter is dirty, it gets clogged and prevents airflow from your furnace to the house. Some furnaces have a built-in feature that will automatically shut off a furnace if the air filter is clogged to prevent overheating. When that occurs, you will feel cold air blowing throughout your house. Either clean or replace your air filter, which can cost anywhere from $3-$15 dollars.

Causes of Furnace Short Cycling2.) Pilot Light & Ignition System Issues

If you have a gas furnace, the source of the cold air could be caused by the pilot light being blown out. When a pilot light goes out, the combustion of gas will not take place. This means that there will be nothing to heat up the air blowing through the furnace and into the house. Just like the air filter, this has a simple fix. If your furnace is not blowing hot air, deactivate the power and turn the pilot light switch to “off.”

To be safe, wait fifteen minutes so that any leftover gas may leave the furnace area. After, turn the switch back to “pilot.” Next, use a lighter or match to light the incoming gas. Once the pilot light has a flame, turn the switch to “on.” Once the switch is adjusted to the “on” position, activate the power to restore the distribution of hot air in your house.

3.) Excess Water Around the Furnace & Condensate Line

If you have a high-efficiency furnace, condensation could be the culprit to your furnace blowing cold air. Condensation usually exits the furnace system through the condensate drain line. If the line is blocked, the furnace’s overflow kill switch will turn the unit off to prevent any water damage. Standing water surrounding your furnace system could be the sign of a condensate line blockage.

To clear the condensate line, first, turn the power to the furnace off. Locate the condensate drain pan and remove the water that sits in the pan. Remove the pan and clean it with dish soap and water and put it back. If your furnace is not blowing hot air, follow the condensate line that extends from below the pan to outside your house. Next, attach a wet/dry vacuum to the opening of the condensate line to suck out any clogs. Once you restore power to the furnace, it should function properly again.

7 Reasons Your Furnace is Blowing Cold Air & How to Fix4.) Thermostat Problems

The reason your furnace is blowing cold air does not always lead back to your furnace. The issue could be your thermostat. A reason that your furnace is blowing cold air could be because of the simple reason that the fan setting is switched to “on.” Usually, fans are switched to “auto.” If your fan is on the whole time, it will blow air regardless of whether the A/C or heater is running. If your furnace is off but you feel cold air, then it might be the fan settings.

Another thermostat issue could be that the battery to it is low. If this is the case, then it might not be sending the proper signals to your thermostat for it to work. This is a common problem in older thermostats. If it isn’t the battery—or the fan—then your thermostat is probably malfunctioning. To determine if this is the problem, turn your thermostat all the way up and turn off the constant air circulator setting. Stand near your furnace and listen for clicking noises. If you do not hear any, then most likely your thermostat is defective. Replacing a thermostat costs anywhere from $112 to $250; the national average price for a thermostat replacement is $170.

5.) Dirty Gas Burners

Along with filters and condensate lines, the furnace gas burner can also accumulate grime and dirt, which can cause clogging. If it is clogged, no fuel will be getting through and into the furnace. Since no fuel is getting in to heat up the air, your furnace may blow cold air.

7 Reasons Your Furnace is Blowing Cold Air & How to Fix6.) Holes in Air Ducts

Having holes in your air ducts could be a more serious reason as to why your furnace is blowing cold air. If there are holes in the ducts in your house, heat energy will escape. By the time the furnace air gets to your room, it won’t be as hot as it was when it was first exiting the furnace. Typically, however, this issue is rare as ducts are long-lasting and durable. This is an instance in which you would need to call an HVAC professional to help you out.

7.) Furnace is Not Receiving Gas

Another easy fix, a furnace not receiving gas happens when the gas line valve is closed or the gas to your home has been shut off. If it is the former, all you need to do is open the gas line valve once again and everything should be back to normal in no time.

Furnace RepairHeating & Furnace Repair Services

No matter what the issue may be, the professionals at ServiceMark are here to help you. From air duct holes to pilot light questions and more, our team has the necessary tools to perform a heating repair on your gas furnace. If you need furnace repair, replacement, or maintenance, give our team a call by phone at (302) 367-7915 to receive support. Give us a call and let us help you get your home warm and toasty in no time!

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