How Does a Car's Heating System Work?

by Steve Smith

Parts of the System

A car heater has several different parts that work together to create heat inside the car. The most important part is the heat core, which is like a radiator. This part traps heat from the engine and then turns it into heat for the passengers in the car. The heat core and the blower motor, another important part, transfer the heat from the engine to the car's interior. This happens thanks to a few other parts that include the coolant, thermostat and heat control valve.


An engine creates a lot of heat because there is a tremendous amount of friction in its working parts. The combustion of gas in the cylinders also creates a great deal of heat. Under normal conditions, this heat is directed away from the motor by the coolant system. The coolant is pumped into the engine and then back out again. It is heated during this process, so as it leaves the engine it is drawing heat away from the engine. In a sense, it is transferring heat from one location to another like a train moving loads of coal or products from one station to another. This has to occur, otherwise the engine will become too hot. Sensitive gaskets and parts can be damaged, and the engine block can crack.

How a Car is Heated

When it is cold outside the heat from the cooling system is harnessed to keep passengers warm. As the coolant is pumped out of the car engine it travels through the heat core. The heat core strips the heat from the coolant (helping to return it to its normal temperature) and the coolant then circulates back into the pump and into the engine. The heat core becomes very hot after several minutes. It is like a boiler and blower. When you want heat inside the car, the blower fan (mounted behind the heat core) turns on and now directs heat back into the car through the open vents, keeping everybody toasty warm.


The thermostat in your car is similar to the one in your home. It detects when a car engine is hot enough to receive coolant. Once the engine reaches a set temperature, the thermostat opens and begins the flow of coolant into the engine. This starts the cooling and heating cycle, as described above.

About the Author

Steve Smith has published articles on a wide range of topics including cars, travel, lifestyle, business, golf, weddings and careers. His articles, features and news stories have appeared in newspapers, consumer magazines and on various websites. Smith holds a Bachelor of Arts in English and journalism from University of New Hampshire Durham.

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