How Does a Car Heater Work?

As the cold winter season approaches, it’s about time to check on the condition of your car heater. Car interior heating is every driver’s best friend when it comes to staying warm and comfortable during those chilly days. To make sure your car heater is functioning as it should, it’s a good idea to understand how a car heater works in the first place.

How Does a Heater in a Car Work?

An internal combustion engine naturally produces heat every time it’s turned on. But how exactly does this heat enter and regulate the temperature inside a cold cabin? Well, it’s all thanks to the car heating system, which consists of the following parts:

• Heater core
• Blower motor
• Heater hoses
• Heater control valve
• Heating, ventilation, and air conditioning (HVAC) control panel

These components work hand-in-hand with the cooling system’s coolant, thermostat, radiator, and water pump. In other words, the vehicle’s cooling system has to work for the heating system to work.

When the coolant passes through the engine, it picks up heat to prevent the engine from overheating. This coolant then flows through the radiator, where the heat is dissipated. However, when you turn on your car heater, the hot coolant flows from the engine to the heater core instead. A fan blows on the hot liquid, triggering a heat exchange that cools down the heater core while heating the air that then goes through the vents to the cabin.

How Do Vehicles Regulate Cabin Temperature?

Older vehicles are usually equipped with a water-valve system that determines how much coolant flows to the heater core depending on the cabin temperature set by the driver.

On the other hand, modern cars tend to use an air-blending system that uses flaps to let in cold outside air to mix with the heated air. This allows the hot air to cool down and reach the desired cabin temperature.

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Why Your Car Heater Isn’t Working

Is there anything worse than a car heater that refuses to work in the winter? Not only is it uncomfortable and distracting, it can also be dangerous, especially in harsh climates. Here are the common reasons why your car heating system might be acting up:

Low Coolant Levels

If your engine is already hot but the heater isn’t blowing hot air, then you’re likely dealing with low coolant levels. Automotive heating systems rely on coolant to function properly, which means insufficient coolant will prevent it from getting hot air into the cabin.

Low coolant is typically caused by a leak in the cooling system, poor maintenance, and air pockets in the coolant. To get rid of these air pockets, you’ll have to bleed the coolant before topping it off with a fresh batch of coolant.

Damaged Blower Fan Motor

Is your auto heater blowing out little to no air even after turning it to the highest setting? This is likely caused by a damaged blower fan motor. It might feel warm inside your cabin, but the air likely isn’t circulating as it should.

When checking the motor, it’s also a good idea to inspect its fuse, resistor, ground circuit, and wiring too.

Malfunctioning Water Pump

If your vehicle’s coolant levels are normal but your cabin still isn’t getting any hot air, consider checking the water pump next. A defective water pump can keep coolant from circulating throughout the cooling system. Not only does this stop the car heater from working, it can also cause the engine to overheat.

Faulty Thermostat

A car with a heater that refuses to blow hot air might be hiding a faulty thermostat under the hood. When a thermostat is stuck open, the engine takes longer to warm up. The engine is likely to stay cold, preventing the heater from releasing hot air into the cabin.

Worn or Clogged Heater Core

The culprit behind the chilly temperature in your cabin might just be a clogged heater core. Over time, coolant will naturally get dirty. If it isn’t changed regularly, dirt can build up and prevent coolant from flowing through the heater core.

A worn heater core can also start to leak, causing coolant levels to drop along with the temperature in your cabin. You’ll have to replace the heater core with a new one.

Stuck Blend Door

When you turn on the heater, the blend door shuts off the airflow from the A/C, allowing only hot air from the heater to enter the cabin. Of course, this also works in reverse. The blend door can block hot air from entering the heater to allow only cold air to flow into the cabin. When the blend door gets stuck in this position, hot air won’t enter from the vents.

If the blend door is fine, inspect the blend door actuator next. The actuator controls the blend door’s movements, which means it can easily stop hot air from entering your cabin if it fails.

How To Keep the Heater in Good Condition

Keeping your car heater in good condition is all about proper maintenance. This includes regularly topping off your coolant and making sure it’s clean. Follow your manufacturer’s recommended mix of antifreeze and water, and watch out for any leaks.

You’ll have to inspect the different components of your car heating system as well, including the thermostat, water pump, radiator, and heater core. Don’t ignore any issues you spot, and consult a mechanic as soon as possible.

How Often Should You Inspect Your Car Heater?

When in doubt, it’s always best to follow your manufacturer’s recommended service interval, but inspecting your heating system at least once a year should be fine. It’s best to do it ahead of winter, so you can be ready before the snow settles. Regular inspections can go a long way in catching any problems before they get worse.

How Often Do You Need New Coolant?

The exact interval can vary depending on several factors, including your vehicle’s year, make, and model. In general, however, it’s best to flush and top off your car’s coolant every 30,000 miles. Keeping coolant levels high and making sure there are no leaks will help your car heater work efficiently.