Heater Control Valve: Description and Operation

The heating system utilizes hot coolant from the engine cooling system to warm air for heating the passenger compartment. The amount of coolant that flows into the heating system is controlled by an electric water valve.

The water valve is electrically actuated. It is located at the left-center back of the engine compartment (beside the brake booster). It controls coolant flow through the heater core. The valve is powered closed by an electric switch; when not powered, it springs open. The valve, when powered closed, prevents hot coolant from entering the heater core, so the air entering the passenger compartment is not heated, When power is removed, the valve springs open, so that hot coolant flows through the heater core and can warm the air entering the passenger compartment.

The E31, E32, E34, E36 (IHKR and IHKA), E38, and E39 cars use pulsed water valves to control the heater core temperature.