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Why is My Furnace Blowing Cold Air? Six Possible Reasons

Homeowner adjusting air vent on upper wall of home

In some parts of the country, like Arvada, it gets very cold come the wintertime and you rely on your furnace to keep your home nice and warm. So when you fire it up and it’s blowing cold air around your home, you start to panic. But you shouldn’t. This doesn’t necessarily mean that you need a new furnace at the most inconvenient time of the year. There are some very simple possible explanations, like a lack of furnace and air duct cleaning, that we’re going to talk through in this article.

Why Your Furnace Might Be Blowing Cold Air

As we just mentioned, don’t start panicking just yet, as often a furnace blowing cold air can be quite simple to fix. Here are some of the more common reasons that it can happen.

You’ve Not Given It Time to Heat Up

Have you come to this page after turning on your furnace for the first time this season? If so, your issue might just be a lack of patience. Your HVAC system will take a few minutes usually to kick into gear and start producing the hot air that will warm your bones. If 15 minutes pass and the air that is being blown out of the vents is still cold, then you can start to think something might be wrong and look at other possible explanations in this article.

Have You Set the Thermostat Correctly?

We’ve seen clients in Arvada make this mistake and then feel rather silly when we’ve come to troubleshoot the issue. We’d always advise that you have it on the “auto” setting. Some people have it simply set to “on” But if you do that, air will be circulated around your ducts even if the furnace is not firing. And that air will be cold…

Set it to auto and air will only be blown around the house when the furnace is on too.

Dirty Air Filter

Some homeowners make the mistake of thinking that their air filters last forever, or at least a lot longer than they actually do.

Over time, your filter will become dirty and clogged. This makes it much harder for air to pass through it. If it gets to this stage, it can cause the heat exchanger to overheat. All furnaces have a safety mechanism in place whereby if this overheating is detected, a “high limit switch” is triggered and the burners will cut out. This is to protect the heat exchanger, as at very high temperatures it can crack. And you don’t want that, as it’s expensive to replace.

A professional furnace cleaning company will check on the filter as part of their service, but as the homeowner, you should also be checking it periodically.

Furnace Overheats for Other Reasons

That same “high limit switch” may be triggered for reasons other than a clogged air filter. Here are some other common issues that could be causing your furnace to overheat.

  • Dirt Accumulating – This is why arranging a regular furnace cleaning is so, so important. Dirt doesn’t just accumulate in the air filter. It can build up in lots of the other components, such as the blower, and when this happens overheating can sometimes occur.
  • Mechanical Fault – Your furnace contains lots of moving parts that all work together to provide the hot air necessary to heat your home. If your furnace is only blowing cold air, it’s possible that one or more parts have failed due to wear and tear and need to be replaced.
  • It’s Just Old – Even if you keep on top of furnace cleaning and maintenance, there comes a time when it will just “give up” and that could be why it’s blowing cold air or won’t work at all. The burner, flame sensor and gas supply are all parts that can cause overheating if not working properly.

Issue with the Gas Valve

This obviously only applies if you have a gas furnace. If so, it could be that there’s an issue with the gas valve and no gas is getting through to be burnt to produce the heat you desire. Sometimes this could be due to a faulty valve, in which case it needs replacing. But other times it can be due to a build-up of dirt inside this valve, which prevents it from working correctly. In this case, a call to a furnace cleaning company is what you need.

Leaking Ducts

It’s possible that your furnace is blowing hot air, but it feels like it’s not because all of that hot air is escaping before it actually gets to you. How is that so? Well, if your air ducts are full of holes or cracks, or your air vents are blocked up, the hot air will be lost. This is why it’s so useful to have an annual air duct cleaning arranged, as these issues will usually be picked up and you can make the necessary arrangements, rather than having to try and “figure it out” once winter has already arrived.

Furnace Cleaning in Arvada that Keeps You Warm

It’s not a good idea to wait until winter to see if everything is fine with your furnace. An annual furnace cleaning can help you to get ahead of any potential issues well in advance. If you’ll like us to give your system the once over, call our service team today at (720) 419-7792.

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