Normal Operation
WARNING: This page is about a different car, the 2006 Ford Pickup, 2006 Ford F550 Super Duty, 2006 Ford F450 Super Duty, and 2006 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
Under normal operation, the automatic temperature control (ATC) solenoid and manifold receives a ground from the electronic automatic temperature control (EATC) module through circuit 1106 (LG/WH). When the heater control valve vacuum solenoid is to be energized, the ATC solenoid and manifold receives power from the EATC module through circuit 1111 (VT).