How Does A Car Heater Work

Driving in cold weather can get quite uncomfortable if the cabin isn’t warm enough. In areas with a lot of snow and hail storms, it would virtually impossible to drive without proper climate control for the interior. A car heater is an essential component to keep passengers warm and toasty while driving. Most car heaters use the heat of the engine to warm the car interior. Other systems make use of an electrical heating element to provide the cabin with warm air. But how car heater works?

Electrical heaters use power from the battery to heat the cabin and do not consume fuel, unlike traditional car heaters which use hot coolant from the engine to warm the cabin.

Let’s look more closely at car heaters.

Essential Components of a Car Heater System

A car heater is part of the HVAC (Heating Ventilation and Air Conditioning) which maintain the optimum temperature inside the vehicle cabin. It is made up of several key components:

  • Heater Core: This component consists of a small radiator which is located underneath the dashboard. Its main function is to absorb heat from the engine coolant and transfer it to the heater system in order to warm up the cabin.
  • Control Valve: The control valve regulates the flow of coolant into the heater core mechanism. The thermostat is used to regulate the control valve.
  • Fan Blower: The fan circulates heat throughout the cabin by forcing warm air from the heater core through dashboard vents.
  • Vents: contain fins and are placed on the dashboard to direct warm air into the cabin.
  • Thermostat: Controls the flow of coolant through the heater core depending on the temperature setting. Opens when more heat is required and closes when the temperature reaches the desired level.
  • Water Pump: a component that circulates coolant through the engine, absorbs heat and then transfers it to the heater core.
  • Hoses: connect various components of the HVAC system such as the water pump, control valve and heater core. Coolant flows through hoses under pressure.
  • Climate Control Switches: The heater controls consist of buttons, knobs and switches to allow the driver to control the heater temperature, fan speed, air flow direction and other settings.

In the case of an electrical heating system in a car, you will have an electric coil that heats up due to resistance, and a fan that blows over it into the cabin to warm the interior. These systems do not use the heat of the engine and are powered by the car battery.

Checkout here What Is Coolant And How Does It Work?

How Car Heater Works?

A car heater warms up the cabin quite efficiently once the engine is running. It circulates the hot coolant from the engine through a heater core (a small radiator-like component) which absorbs heat from the coolant and warms up the air blown across it with a fan. The warm air maintains a comfortable temperature inside the cabin by blowing through a series of air vents placed in the dashboard.

Here is a step-by-step explanation of how the heater warms up the cabin:

  • The engine is turned on and starts to produce heat due to internal combustion. Coolant is continuously circulating around the engine block and absorbing the excess heat.
  • The water pump circulates this hot coolant to the heater core. The heater core contains small tubes that act as a radiator. This heat is transferred to the heater core and its temperature rises.
  • A fan blows air over the heater core, picks up the heat and is forced through vents in the dashboard, floor and near the windshield. The cabin stays at a comfortable temperature so that passengers can drive through a cold climate.
  • The thermostat is set at a desired temperature. It regulates the control valve which allows coolant to flow into the heater core. When the temperature drops in the cabin, the thermostat sends a signal to the control valve to open and admit coolant into the heater core. The air warms up and the temperature reaches its desired setting. At this point the thermostat records the temperature and sends a signal to the control valve to close and stop sending coolant into the heater core, reducing the amount of heat generated by the system.

Read here about how to change your engine coolant.

An electric car heater is another type of system using electricity to generate heat rather than using heat from the engine. The electric heating element consists of a coil which is made up of resistive metal. When electricity flows through this coil, a large amount of heat is generated. A fan blows over this heating coil and distributes warm air throughout the cabin. Electric heaters have the advantage of working even when the engine is off and can generally maintain a more constant level of temperature, although they do consume battery power.

Also Checkout How To Deal With Car Engines Overheating

Important Reasons Why We Use Car Heaters

There are several advantages to having a car heater in your vehicle. Listed below are important reasons why car heaters are standard on most vehicles:

Keeping the Interior Atmosphere Comfortable:

During cold weather, passengers are kept warm and cosy with the help of a car heater. So, the primary reason we use car heaters is to maintain a comfortable atmosphere in the cabin temperature while driving through the cold climate.


It is common for windscreens and windows to frost up in a snowstorm. Car heaters can direct warm air at the windshield to demist and defrost ice build-up, thus increasing visibility and reducing the risk of accidents.

Engine Warm-up:

A car heater can warm up the engine quickly after a cold start, which can help improve fuel efficiency, performance and reduce chances of stalling in cold temperatures.

Passenger Well-Being:

Cold-related illnesses such as hypothermia and frostbite are prevented with car heaters. Occupants do not have to wear gloves or sweaters in the vehicle.

Click here to checkout Everything About Engine Flushing Systems


Modern cars are equipped with sophisticated heating and ventilation systems which allow a constant flow of fresh, climate-controlled air to circulate throughout the interior. The car heater plays a crucial role in maintaining passenger comfort, safety and improves the driving experience, especially through cold weather and snow storms. With advanced technology and electronics, car heaters are extremely efficient and user-friendly. Drivers can adjust cabin temperature with the click of a button and adjust air flow direction to areas that require warming up. With a properly working car heater, you can enjoy your drive even through the coldest days of the year.

If you found this article informative and interesting, you may also want to read about Learn How An Engine Cooling System Works + Maintenance or The Signs Of Bad Ignition Coils In An Engine or visit carorbis blog for more information like this.

Frequently Asked Questions

Q1. How Does Car Heater Work?

Ans. The heater in your car is connected to the coolant, radiator, thermostat, water pump and HVAC system. The heat of the engine is transferred into the coolant inside the HVAC system. A component called the heater core absorbs excess heat from the radiator and starts to get warm. A blower fan forces air over the heater core, through the cabin vents and into the car interior to keep passengers warm. The interior temperature can be regulated by adjusting a valve that controls the flow of coolant through the heater core. Some cars have a different heating system which uses an electric heating element to provide heat in the cabin without running the engine.

Q2. What Are Some Car Heater Problems?

Ans. Some issues that can occur with a car heater include a blocked heater core, leaking coolant, faulty thermostat, electrical issues, clogged air filter, blown heater core valve and a defective heater fan blower. The heater core should be free from debris, otherwise, the hot coolant will not be able to flow through it properly. When the coolant level drops due to a leak, there will not be enough heat transfer in the heater core. When the thermostat fails to work properly, coolant may not flow through the heater core efficiently. An electrical issue may prevent the heater from turning on or the fan blower may stop working. Finally, if the air filter is clogged, the fan blower will not be able to push ait through it into the cabin.

Q3. How to Turn on Car Heater?

Ans. The process of turning on a heater can vary depending on the make and model of the vehicle. First, start the engine, and as it heats up, the warm coolant will make its way into the heater core. Adjust the temperature with the heater control dial on your dashboard. Switch on the fan to allow warm air to flow from the heating element into the cabin. Don’t forget to change the settings to the heater on your climate control. Some cars have a heater powered by an electric heating element that doesn’t require the heat of a running engine to warm up the cabin.

Q4. Why Does Car Heater Blow Cold Air?

Ans. A faulty heater core will not be able to exchange heat from the coolant into the HVAC system. This could be due to a faulty thermostat which prevents coolant from flowing into the heater core. Another reason why car heaters start to blow cold air is due to low coolant levels. In this case, the heater system will not be able to circulate warm coolant through the heater core, resulting in cold air blowing through the vents. An electrical issue could also cause the heater core to malfunction by preventing the thermostat sensors and other electrical components from functioning properly.

Q5. How to Fix a Broken Car Heater?

Ans. Inspect the heater core radiator for debris that may be blocking coolant from flowing through the system. The air filter should be clean and free of dirt for smooth airflow through the heater. Top up coolant levels if they are low (there could be a coolant leak, so confirm that the system is intact). Sometimes a blown fuse may cause the heater to stop working. The heater fan should be working if you want warm air to flow into the cabin, so ensure that it is working properly. The heater system has a heater control valve which allows coolant to flow in as required. Check the valve for proper functioning to rule out all issues with the heater.

Q6. Which is the Most Commonly Used Car Heater?

Ans. The most common type of heater used in a car uses the heat of an engine to warm up the air inside the cabin. It uses hot coolant to transfer heat to the heater core system. This is known as a water-based or liquid-based heater and is typically used on cars, SUVs, trucks and other vehicles that have an enclosed cabin. This type of heating mechanism is used because it is a simple system, inexpensive to manufacture and easy to install in a vehicle. The heat produced by this system is useful in cold climates where the engine can continuously warm up the cabin without straining the engine or consuming more fuel.  Electrical heaters in cars are less common because they are expensive and consume more power.

Q7. Can a Car Heater Be Repaired or Does It Need to Be Replaced?

Ans. In most cases, a car heater can be repaired instead of replaced. However, the extent of repairs will depend on a specific problem with the heater mechanism. Low coolant levels can easily be topped up, while a faulty thermostat or sensor can be repaired without a problem. Even clogged heater cores can be flushed with chemicals to free them up. However, more complex problems such as a worn-out fan motor, corroded evaporator or faulty electrical system may need a replacement of components, and in some cases even the whole heater unit.  Since these are complicated systems, it is best left to an HVAC technician to diagnose the problem.

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