What to Do About a Furnace That Won’t Turn Off and Is Blowing Cold Air

furnace won't turn off blowing cold airRecently, we had a problem with our garage door. The mechanism that makes it open and close with just the push of a button stopped working. Now, we could have just forgotten the dang thing and started operating the door manually, but this thing has one simple job to do: open and close a door. If it’s not doing its job, it’s time to get it fixed.

This is something I see a good deal in my own work as a Sacramento HVAC professional—furnaces that stop doing the one thing that they’re tasked with, i.e. heating up a house. That’s why I’d like to take a few minutes to talk now about how to handle a furnace that won’t turn off and is blowing cold air. The chilly season is upon us here in Sacramento and it does get kind of cold, even if it never quite gets cold enough to snow or freeze.

Let’s discuss the causes behind furnaces blowing out cold air that you can’t turn off, some of the small things that you as a homeowner can do to check out what the problem may be, and, ultimately, the best way to get your faulty furnace fixed this fall and winter. I know the easiest thing for you to do is to try to live with and ignore these problems, but, take it from me, it’s best to take care of them as soon as possible. Otherwise, they’ll only get worse, costing you both time, money, and the comforts of home.

Possible Causes of a Furnace That Won’t Turn Off and Is Blowing Cold Air

We’ve talked in the past about the causes behind air conditioners blowing hot air, but today I’d like to discuss the opposite: a furnace that won’t turn off and is blowing cold air. There can be many reasons for this, but there are three common ones.

furnace is blowing cold air and I can't turn it offHere are the three most common causes of a furnace that won’t turn off and/or is blowing cold air into your home:

  • Your thermostat is set to FAN ON: Now, I know this one sounds obvious, but the fact of the matter is that I’ve been on my fair share of calls where the furnace won’t turn off and is blowing cold air because the thermostat is set to the FAN ON position. Once the house has been heated to 68, 72, or whatever temperature you have your heat set to, your HVAC will then revert to blowing the fan, which is unconditioned air. In the chilly season, this unconditioned air can definitely feel like it’s on the cold side.
  • The furnace is overheating: This next one sounds like it’s impossible. How can a furnace, that’s designed to get hot, overheat, right? Well, it can. Furnaces have something called a limit switch that makes sure they don’t get so hot that they become dangerous. When the limit switch activates, it turns a furnace’s burners off—but the air continues to blow. As with the fan problem above, in the fall and winter, this unconditioned air will probably feel pretty cold. We’ve talked about the importance of furnace filters many times before, but it’s worth noting here again: If a filter gets too dirty, it can block airflow, causing your furnace to overheat.
  • The pilot light is out: This one is very simple to diagnose. Sometimes, a furnace will start blowing cool air because the pilot light has gone out and might need to be relit.

Now let’s talk solutions for the causes behind your furnace blowing out cold air nonstop.

Homeowner Tips for Fixing a Furnace Blowing Cold Air Nonstop

Now that we know what some of the causes are for a furnace that won’t turn off and is blowing cold air, let’s take a quick look at the small things that you as a homeowner might be able to do to fix the issue, at least temporarily.

As you’ve probably surmised, if the fan being set to ON is the problem, all you have to do is adjust the settings to AUTO or OFF to clear up the issue. So, we won’t spend too much time on that one.

The second problem—an overheating furnace—is a fairly easy fix, too—or at least it can be. The first task here is to check to see if you have a dirty or clogged filter. If so, you need to switch it out with a fresh, clean one, or find a local HVAC maintenance and repair company that can put you on an automatic filter change schedule so that you don’t have to worry about it.

If the filter isn’t to blame, though, my advice is to call an HVAC company ASAP because you might have a larger problem on your hands. That’s actually the same advice I have for your pilot light being out, too. Go ahead and relight it once, but if it goes out again, it’s time to call a pro to check things out.

How to Fix a Furnace That Won’t Turn Off When Blowing Cold Air

In our last section here, I want to stress the importance again of calling out a local Northern California HVAC heating and cooling company to help you when you have a furnace that won’t turn off or is blowing cold air. The thing is, furnaces are tricky. There are many things that can be wrong—and fixing most common problems can be complex.

If your pilot light continues to go out, for instance, the issue could be something as simple as the gas valve switch not being set to the ON position, or it could be as complex as having a problem with something called the thermocouple rod, which is the copper piece you see the pilot flame hitting. That kind of work can be a very dangerous DIY job, which is why this is one issue I highly recommend turning to a pro for help with.

So, there you have it. Your furnace is really meant to do one thing for you: blow out warm air that makes your house comfortable in the fall and winter, whenever you ask it to. If you find yourself with a furnace that won’t turn off and is blowing cold air, well, then, you might have a problem that needs to be fixed. There’s no shame in calling a professional to take care of it for you. In fact, that’s exactly what I recommend.

Also, depending on how old your furnace is, you may want to start having a conversation about whether it’s time to replace your HVAC system. The best local heating and cooling companies will offer a free evaluation and an estimate for that kind of a project. They can also help you navigate the many financing options available here in Northern California for folks who want to make energy efficiency upgrades to their home. I know that at Bell Brothers, it’s one of our favorite topics of conversation!

At Bell Brothers, we’re community locals we’ve been helping folks in Sacramento take care of their heating and cooling problems for years. Contact us today to schedule a free in-home consultation.

Wondering how to finance a new furnace, or maybe even new windows and plumbing? HERO is a unique financing option that helps California homeowners afford energy efficient upgrades to their home. Contact Bell Brothers, a HERO-approved contractor, to learn more. Our local HVAC, plumbing, and window specialists will walk you through the entire process, from applications to installation.

Image courtesy Catalin Pop