Electrically Controlled Heater Control Valve:
1. Input: The valve receives a signal from the vehicle's climate control module (CCM). This module, based on the driver's temperature settings and other inputs (like outside temperature sensor readings), determines whether coolant should flow to the heater core.
2. Solenoid Activation: The CCM sends an electrical signal (typically 12V) to the heater control valve's solenoid.
3. Valve Position: The solenoid energizes, moving a valve pin or plunger within the valve body. This opens or closes a passage, allowing or restricting the flow of coolant from the engine to the heater core.
4. Coolant Flow: When the solenoid is energized, the valve opens, allowing hot coolant to flow through the heater core. This heats the air that passes over the core, and that warm air is blown into the cabin. When the solenoid is de-energized, the valve closes, stopping coolant flow to the heater core, and preventing heat from entering the cabin.
Vacuum-Controlled Heater Control Valve (Less Common in Modern F-150s):
Older F-150s might use a vacuum-controlled valve. The operation is similar but uses vacuum instead of electricity:
1. Vacuum Signal: The vacuum signal comes from the engine's vacuum system, controlled by a vacuum switch operated by the HVAC system.
2. Diaphragm: The vacuum acts upon a diaphragm inside the valve.
3. Valve Position: When vacuum is applied, the diaphragm moves, opening the valve to allow coolant flow. When the vacuum is released, the diaphragm returns to its resting position, closing the valve.
In short: Regardless of whether it's electric or vacuum, the heater control valve acts as a gate, controlling the flow of hot coolant to the heater core, ultimately determining how much heat is directed into the cabin of the F-150. The system is designed to precisely control the temperature based on the driver's selection.
