What to Do When Your Car Heater Blows Cold Air

car heater blowing cold air

In most parts of the country, winter is in full swing, even if it is a bit dry this year. But dryness doesn’t mean that it’s any less cold, so the last thing you want to deal with this season is a faulty car heater. With that in mind, today’s post is focused on what to do in the event your car heater suddenly stops working.

Remember that in some especially cold regions a malfunctioning heater is potentially dangerous, so even if your car heater is working properly, it’s smart to plan ahead. Make sure to pay special attention to the section of this post that discusses what safety items to keep with you during winter travel. You should also make sure you’re a member of a reliable roadside assistance program before heading out.

For more cold-weather driving tips, check out these other posts from the blog as well:

Now, back to the matter at hand. What should you do when your car heater blows cold air?

vehicle heating system problems

Check Your Coolant Levels First

Coolant isn’t often something we think about during the cold months, but it’s just as important during the winter as it is during the summer—in fact, coolant is responsible for your heater’s operation.

Here’s a very brief explanation of how your heater works: coolant isn’t actually cool (or shouldn’t be). The purpose of coolant is to absorb the heat from your engine. Therefore, “hot coolant” means a cooler engine. Coolant is then routed to your heater core. A fan pushes air over the heater core into your vehicle.

With that in mind, you can see that if your coolant levels are low, your heater will blow cold air, or at least the air won’t be as warm as you’d like it to be. Furthermore, you’re also at risk for a too-hot engine. If you have a car heater problem, check your coolant levels first.

Make Sure Your Thermostat is Working

If your coolant levels are fine, the next step is to check if your thermostat is working properly. This is pretty easy to determine—after running the car for 5-10 minutes, check the temperature gauge on your dashboard. If it stays at the bottom (where the “C” is), odds are your thermostat is broken or malfunctioning.

The thermostat is responsible for “telling” the car that the engine coolant is hot enough to be sent over to the heater core. If the thermostat isn’t working, the coolant won’t go to your heater core, and your heater will blow cold air. The good news? Thermostats are usually a pretty cheap replacement.

Check For Water Leaks

It’s possible that a water leak is responsible for your car heater blowing cooler air. Unless it’s a full-blown leak, the air won’t likely be strictly cold, but you may notice it’s less warm than it should be. Water leaks can crop up at different places throughout the vehicle, such as the radiator, water pump, or any associated hoses. Check them all for signs of leakage.

troubleshooting car heater problems

The Heater Controls Themselves

While less common than the other issues discussed above, it’s possible that the heater controls inside your car are the problem. Sometimes, especially in older vehicles, the controls can get clogged by debris or simply wear out from repeated use. If everything else looks fine, but your control buttons/dials “feel off” inside, that might be the cause of the problem.

You may also want to check the heater control valve, which is essentially the switch under the hood that’s responsible for responding to your in-cabin button presses to turn the heat on or off. If it’s not working, your heater won’t know it’s supposed to turn on.

Malfunctioning Heater Core

When all other simple possibilities for the heating problem have been ruled out, it may be that you have a faulty heater core. These problems don’t always necessarily require a replacement—often they’re as simple as a clogged coolant tube or a stuck fan.

If there’s a problem with the heater core, you’ll likely experience other problems or signs, such as rapid use of coolant, overheating, or weird smells (in this case it’s coolant, a sweet smell). If you experience any of these signs, replace your coolant and take your vehicle to a repair shop.

How to Get Help For a Broken Car Heater

Some of the fixes discussed above are easy enough to check and possibly even repair on your own, but some of them may require professional help. If you’re looking for a professional auto service you can trust, make sure to find your local BG-certified service center. Stay warm out there!

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