Heater Control Valve: Description and Operation

HEATER BYPASS VALVE

The heater bypass valve is a spring-loaded valve inside of the bypass valve housing. The heater bypass valve controls the volume of coolant flow through the heater core. At low coolant flow rates, the valve remains closed, and all of the engine coolant passes through the heater core. At increased engine speeds, the valve begins to open. Upon opening, the valve limits the maximum flow of coolant through the heater core to 5-6 gallons per minute by bypassing any excess coolant. Limiting coolant flow through the heater core in this manner prevents the long-term erosion and corrosion that can result from excessive flow rates. However, an adequate amount of coolant remains available for all heat requirements.