Reasons Why Your Car Heater Isn’t Blowing Hot Air

  • Oct 12,2020
Person feeling air out of car vent Person feeling air out of car vent

You jump in your car on a cold, wintery morning and crank the heat up. But after a few minutes, you notice it still isn't blowing hot air! What gives? Learn what's keeping you from enjoying your car's warm air and what you can do about it.

Contaminated Coolant

Engine coolant contains a precise mixture of antifreeze and water, which helps keep your engine from overheating or freezing. If your car’s coolant has the right ratio of antifreeze and water, it shouldn't freeze in the winter or get too hot in the summer, ensuring that your car’s cooling system can effectively absorb and dissipate excess heat created in the engine.

When you run your car’s heater in the colder months, some of this excess heat is blown into the cabin to help you stay warm and defrost your windshields! Over time, contamination in your cooling system can make your coolant more susceptible to freezing, which may result in your engine overheating and your heater not working!

Faulty Heater Core

The heater core looks (and works) similar to your car’s radiator — it's made up of a series of narrow tubes and fins. However, while the radiator dissipates heat to the surrounding air, heat from the heater core is blown into the passenger compartment by a blower fan.

The heater core’s maze-like network of tubes is susceptible to clogging and leaks, reducing the coolant level or flow through your engine’s cooling system. Faulty heater cores and low or contaminated coolant levels often come hand in hand, and both issues may lead to your engine overheating and your heater not blowing hot air.

Other signs of a faulty heater core include a sweet-smelling scent in your car, windows that become particularly fogged-up, and puddles under the dashboard or on the passenger-side floorboard.

Malfunctioning Thermostat

Your car’s thermostat is a valve that opens and shuts to regulate the coolant flow to the engine and radiator. Although it’s a pretty simple device, a functioning thermostat is vital to keeping your engine running at optimum temperature.

A damaged thermostat may become stuck in the open or closed position. When stuck open, the thermostat may allow too much coolant to flow, preventing your car from reaching its optimum operating temperature, thereby causing a decrease in performance. On the other hand, a thermostat that’s stuck in the closed position won’t allow coolant to circulate, interrupting the system that cools your engine and heats your cabin. Yikes!

Inoperative Blower Fan

When you crank up the heat in your cabin, the heater core captures heat from the coolant and transfers it into the cabin in the form of warm air. The blower fan is responsible for ventilating that warm air from the heater core through your car’s vents! However, when the blower fan is not working correctly, you may notice little to no airflow coming from the vents.

Various issues may cause your blower fan to malfunction, including a blown fuse or damage to the blower fan’s internal components. Regardless, if you can barely hear or feel a breeze when your car heater is running, issues with the blower fan may be to blame!

Get Cozy When Dashing Through The Snow!

It’s hard to enjoy the ride when your teeth are chattering! Plus, many of the same issues that prevent your car’s heater from blowing hot air can also lead to engine overheating and decreases in performance!

Get a professional opinion on what’s causing your car heater to malfunction and which services and repairs can help fix it at your nearest Firestone Complete Auto Care. With thousands of locations across the country, we’ll get you back en route to your holiday getaway in no time!

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