Maybe the one thing worse than no heat coming through your vents in the winter is having a cold air circulate through your home in Camp Hill, PA, instead. When you want your house warm, cooling is not only uncomfortable — it indicates a problem with your HVAC system. 

Fortunately, you may not need to call anyone for furnace repair just yet. In this article, we’ll go through four common reasons your furnace is blowing cold air. You can fix two of them yourself!

But, if you have any questions or need a professional, call Air Comfort Technologies today. We handle service, tune-ups, repairs, and emergency heating and cooling calls in Central Pennsylvania, and we’ll get you warm again as soon as possible! 

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Four Possible Reasons Your Heater is Blowing Cold Air

If you’re getting cooling when your furnace should be running, check for these problems: 

  1. Wrong Thermostat Settings
  2. Blocked or Crowded Vents
  3. Clogged Air Filter 
  4. Oversized Furnace

Wrong Thermostat Settings

If your thermostat is set incorrectly, or the battery is low, you could get cold air when you want heat. Less common, but possible, is a problem with the wiring.

We’ll start with the simple problems. First, check for a low battery warning. Without enough power, it’s possible the gauge isn’t getting the right readings. Or, it’s sending the wrong message to your HVAC system. 

Next, double-check that you’re on Heat rather than “Fan Only” or “Cooling.” Obviously, cooling is for AC. But, “Fan Only” circulates the house’s air without adding any heating or air conditioning. So, if it’s cold inside, you get cold air through the vents. 

Either way, it’s easier than you think to leave your system one setting and forget to change it when the cold weather starts rolling in. 

If you have a new thermostat or get this problem all the time, a mismatched wire could be the problem. You can remove it and check the connections if you’re handy. Make sure everything’s in the right place — they’re often color-coded. Or, call a professional if you don’t want to tinker with the electronics. 

Blocked or Crowded Vents

Next, locate all the vents in your house and make sure you have 18 inches of clearance around each one. If you don’t, heat can be backing up through the ductwork, which causes a bigger problem. 


Believe it or not, the appliance in your house that generates heat can become overheated! The inner workings of your heater are designed for generating warmth, not housing it. If the temperature in there gets too high, parts can stress, crack, and break. 

Your system has a failsafe, though: Cool air. If it gets too hot, the heater sends a blast of cold through the system to regulate the temperature. When there’s only a temporary issue, this does the trick. But, letting it happen too often causes a much bigger problem. 

If your system has to do this too often, the sudden and drastic temperature shifts will also damage the parts. In particular, the heat exchanger can crack. When this happens, carbon monoxide can leak into your home. 

Since this gas is poisonous, it’s a huge deal. And, you can’t fix a cracked heat exchanger. It’s expensive to take the furnace apart, and then there’s no guarantee a patch will hold. When his part goes, you’re looking at buying another system.

Clogged Air Filter

Dirty Air Filter HVAC Repair in Hanover, PAYour air filter traps dust, dirt, and other particles, so they don’t circulate all through your house. But, if you don’t change it every month or so, it clogs up. If you leave it long enough, eventually, air can’t get through the screen, either. 

When that happens, the warmth that’s trying to escape your system can’t get through. So, you have the same problem as blocked vents: Overheating. 

If you haven’t switched out the filter in a while, do so now. The cloth was white when it went in. If it’s dark grey or completely covered in dirt, you’ve likely found the problem. 

Oversized Furnace

With an oversized furnace, backed-up heating is once again the problem. Unfortunately, this time there’s no easy fix. But, we’ll go through what’s happening, so you know what to expect. 

Let’s say your vents are clear, and the filter is clean. But, your system is way too strong for the house. So, it sends a huge blast of hot air through the house. There’s not enough space for it to circulate, which causes it to once again back up into the system. 

If you notice short-cycling — the heater turns on for just a minute, turns back off, and does this ten times or more an hour — then you’ve likely found the problem. And unfortunately, this problem took hold before the system was even installed. 

At some point, someone made a bad call. Perhaps a contractor did a lousy load calculation on the house and ordered a furnace that was too powerful. Or, a previous homeowner thought bigger was always better, and no one thought to tell them they were wrong in this case. 

Whatever the reason, you now have a furnace that’s too strong for your house. And, it will likely break down earlier than expected. If you don’t end up with a cracked heat exchanger, the moving parts will wear out much faster than usual from all the extra stopping and starting. 

Sometimes, you can extend your ductwork, so there’s more exhaust. But, that’s expensive, takes up a lot of room, and not always feasible. Unfortunately, the solution is usually to get a new system altogether. 

You can wait until it breaks down, but then you’re in an emergency heating and cooling situation. At least, get to the root of the problem and make your plans in advance. You’ll save time and money this way. 

Furnace Repair in Camp Hill, PA

If your heater’s blowing cold air and you can’t get it to stop, don’t ignore the problem! Call Air Comfort Technologies for furnace repair today! Not only will we make sure your Camp Hill, PA home is comfortable again, we’ll make sure you’re not looking at an emergency eating and cooling call for bigger problems later. 

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