Why Is Your Car Heater Blowing Cold Air?

Hannah DeWitt
Dec 28, 2021 · 3 min read
As the weather gets cooler, many are looking for ways to stay warm in the car. Thankfully, even if you don't have a heated steering wheel or seats, your car likely has a heater that can help. Heaters can run into some issues that may need to be repaired, though, and one common issue is a car heater blowing cold air.
Even though a heater blowing cold air can be frustrating, it’s a common problem, and it often results from one of a few issues. According to Lifewire, there are four common causes of the problem.
Black car dashboard with air control dials
Car heaters blowing cold air is a very common issue.

Thermostat is stuck

The thermostat is a valve, and if the valve gets stuck, it could result in the heater blowing cold air. This can happen if the engine's coolant reaches a certain temperature without the thermoses opening. With the thermostat stuck, the circulation of the coolant can be affected.
Once this occurs, the heater may blow cold air. An engine could also be slow to warm up with a stuck thermostat, or it may not correctly warm up at all. 

The cooling system has air in it

Air in a car's cooling system can get stuck, which also affects how the climate control system functions. When this happens, even if you have the heat turned on, the air might come out cold.
Thankfully, this is an easy thing to fix. Flushing out all the air bubbles is all that it takes to get the heat back on in this situation.

The heater core is plugged

If coolant doesn't flow through the heater core, the climate control system will only blow cold air. This is another problem with an easy solution, as once the heater core is unblocked, the heater should work again.
It is also something that you can check on your own easily. A non-contact thermometer can show if a heater core is plugged by showing whether coolant is flowing.

Coolant isn't flowing through heater core

While a plugged heater core may be the result of corrosion, a blockage can occur for a number of reasons. Lint, dirt, pine needles and more can build up in the heater box, and once this happens, your car may only blow cold air. 
This is a maintenance issue that you can also take care of on your own fairly easily. All that you need to do is take out the heater box and clean out whatever junk is blocking it.
These are four common causes of a car heater blowing cold air, but there are other reasons that it can happen as well. You may be experiencing a vacuum issue or some other problem. It can depend on the particular quirks of every vehicle, and some issues, like white smoke from your exhaust, are just unpredictable. 

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