Mountaineer 2WD V8-4.6L SOHC VIN W (2003)
Heater Control Valve: Description and Operation
HEATER CONTROL VALVE
The heater control valve is actuated by the heater control valve vacuum switch (manual climate control) or the heater control valve vacuum control
circuit (DATC). when the heater control valve is closed (full vacuum), coolant flow through the heater core is shut off and A/C cooling efficiency is
increased.