1978-79 Ford Ranchero/T-Bird/Cougar/LTD II A/C-Heat Vacuum Line Routing Diagram

This is page 54, titled "A/C - HEAT (VACUUM)," from a Ford Motor Company factory vacuum diagram manual (footer code FMC-09-78/VF). It applies to the XR-7, LTD II, T-Bird, Cougar, and Ranchero. The diagram shows the complete vacuum routing for the air conditioning and heater system: manifold vacuum source (dark blue hose) through a check valve to a vacuum tank, then via black hoses to the function control valve and temperature selector. The function control valve schematic shows switch positions (A/C, Economy Vent, Hi/Lo, Heat, Defog, Off, Defrost) and the color-coded hoses leading to five vacuum motors: red/yellow to the heat-defrost vacuum motor, orange to the A/C-heat partial vacuum motor, blue to the A/C-heat full vacuum motor, green to the heater water vacuum motor, and white to the outside-recirculate air vacuum motor. Connector pinout legends give hose color order at the function control valve (blue, yellow, orange, green, red, turquoise, black, white, purple) and temperature selector (black, turquoise, purple). A cutaway of the HVAC plenum identifies the heater core, A/C evaporator core, blower, heater water valve, cable-controlled temperature blend door, and the air doors directing flow to defrost, floor, and instrument panel outlets.