The heater core valve is a device that allows coolant to flow into a vehicle's heater core to produce heat. In a vehicle, the heater core is nothing more than a miniature radiator that receives hot coolant from the vehicle's engine. A heater core valve is located in the feed line of the heater core and opens and closes to control the flow of fluid coming from the vehicle's engine. When the heater is not in use, the valve remains closed to prevent hot fluid from reaching the heater core and heating the vehicle's interior. When the heater is switched on, the valve opens and allows hot liquid into the heater core, which in turn warms the vehicle as the heater blower forces air through the heater core and into the passenger compartment.
The typical automotive heater is controlled by adjusting the flow of warm engine coolant or anti-freeze mixture through a copper or aluminum heater core. The heater core consists of rows of tubes connected by thin metal fins. As the heater core valve opens, coolant is allowed to be pumped out of the engine block and into the heater core by the vehicle's water pump. The warm coolant radiates heat through the heater core's tubes and fins, where it is forced into the vehicle's passenger cabin by an electric fan. The heater core valve acts much like a thermostat in that it regulates the amount of heat produced by the heater through the amount of fluid it allows to flow into the heater core.
If not for the heater core valve, the vehicle's heater would be in a continuous state of warming. As the coolant flows through the heating system, the heat from the incoming coolant would radiate into the vehicle's passenger compartment. This would affect the efficiency of the air conditioning system as the cold air would be competing with the warm air in an attempt to exit the vehicle's heating and cooling vents.
Often, when a vehicle is over-heating, it is possible to use the vehicle's heater to aid in cooling the engine down. By turning the heater on, the heater core valve will open, causing the coolant to be redirected from the engine block into the heater core. As the heater's blower pushes air through the heater core, it acts like an additional radiator and cools the engine by removing some of the heat out of the coolant via the heater.