The heater control valve (sometimes called the water flow valve) controls the flow of coolant into the heater core from the engine.
Heater control valves are operated in three basic ways: by cable, thermostat, or vacuum. Cable-operated valves are controlled directly from the heater control lever on the dashboard.
Cable-operated heater valve used to control the flow of water or coolant through the heater core.
Thermostatically controlled valves feature a liquid-filled capillary tube located in the discharge air stream off the heater core that senses air temperature and modulates the flow of water to maintain a constant temperature regardless of engine speed or temperature. Most heater valves utilized on today's car are vacuum operated. These valves are normally located in the heater hose line or mounted directly in the engine block.
To replace a heater control valve:
- Refer to your vehicle's service manual to locate the valve.
- Drain or lower the fluid level in the cooling system.
- Unclamp, unbolt and unplug the valve.
- Reverse procedures to complete installation.
Identify the heater control valve carefully. It is easily confused with other parts.