When it gets cold in the Houston area, the last thing you want to be asking yourself is, “Why is my car heater blowing out cold air?” If you do find yourself in this position, however, there are several things in your car that you may want to check.
Learn what might be causing your car heater to be blowing out cold air from the same people you call after googling things like “car heater repair near me,” “can low oil cause overheating,” and “my car air conditioner is making noise.”
Checking your knowledge of how an engine works
Before we get into diagnosing why your car heater is blowing out cold air, it’s important to go over how your heater gets heat in the first place. And to understand how the heater gets heat, you have to understand how your engine works in the first place.
A healthy engine functions best between 195-220 degrees. Of course, when it’s hot out, there is a potential for your car’s engine to overheat — that’s where coolant comes into play. Your car’s coolant system circulates coolant and water around the engine and through the cooling system to keep things at the optimal temperature.
But how does the engine ever get warmed up if there’s coolant constantly surrounding it (especially if it’s cold out)?
Enter the thermostat.
Your car’s thermostat keeps fluids from circulating in the coolant system until the engine reaches the right temperature. At this point, the thermostat opens and allows the coolant/water to flow. Your thermostat is actually the root of most car heater problems — but we’ll get to that in a minute.
Once your coolant is flowing, your car’s heater can use the heat generated by the coolant to blast you with warm air.
Checking your coolant
Will low coolant cause low heat? Yes. In fact, running low on coolant (a mixture of water and antifreeze) will cause low heat in your car. If there’s not enough coolant, however, you could wind up in a situation where you have a car heater blowing cold air and a car that’s overheating.
To put it another way, when you ask us, “Why is my car heater not getting hot enough?” it’s likely not the “heater” that’s the culprit — but the coolant.
Note that checking your coolant isn’t a required part of your state inspection, so you and your local mechanic will need to keep an eye on it. (For more on state inspections, read our post on the Texas inspection sticker grace period or our post answering the question, “Will my car pass inspection with the airbag light on?”)
Checking your thermostat
Now you know how your heater gets its heat. But surprisingly, your coolant isn’t typically the reason behind your car heater not blowing hot air. In fact, the number one culprit for a car heater blowing out cold air is your thermostat.
If your thermostat never registers that your engine is warm enough or has failed and is either stuck open or closed, it doesn’t allow the coolant to flow. When your coolant isn’t flowing, your heater doesn’t have its heat source. When you take your car to a mechanic for a car heater that’s blowing out cold air, a car heater that’s blowing cold air when idle, or a car heater blowing cold air intermittently, one of the first things they’re going to check is the thermostat.
Checking for water leaks and air pockets
If your thermostat is working your heater may be blowing out cold air because you have a coolant leak.
Should a coolant leak be suspected, your mechanic will check the cooling system for leaks. Part of the cooling system is the heater core which is like a miniature radiator inside your dash. Signs of a heater core leak include foggy windows and damp carpet under the dash as well as a sweet odor.
Checking your heater
Yes. Your heater may, in fact, not be working because the heater itself is broken. While problems with the heater itself are rare, if all other potential possibilities have been tested, your mechanic can check for clogs in the heating system or for issues with the heater controls.
Is your car heater blowing out cold air?
A car heater blowing out cold air can mean more than just an uncomfortable trip to the store and back. Whether your car heater is blowing out cold air all the time or your car heater is blowing cold air only sometimes, it’s wise to get the root of the problem diagnosed and fixed before your heater problems turn into engine or radiator problems.
Need help diagnosing why your car heater is blowing cold air? Colony One Auto Center is here to help. With over 250 years of combined experience and 250,000 cars serviced since 1991, we have the know-how needed to fix your heater.