Ford 2003 Mustang Workshop Manual page 3235

COOL (blue) to WARM (red) causes a corresponding movement on the air temperature control
door and determines the temperature that the system will maintain.
The A/C heater function selector switch combines a vacuum selector valve for direct control of
the vacuum control motors and electrical input to the instrument control module.
Control System Outputs
Blower Motor Switch Resistor
The heater blower motor switch resistor has the following features:
The assembly is located on the passenger side of the plenum assembly behind the glove
compartment (06010).
Three resistance elements are mounted on the resistor board to provide four A/C blower motor
speeds.
Depending on the heater blower motor switch position, series resistance is added or bypassed
in the A/C blower motor circuit to decrease or increase A/C blower motor speed.
An overheating protective device (thermal limiter) will open the resistor coil circuit when the
temperature reaches 105°-110°C (221°-230°F), interrupting the blower motor operation in all
speeds except HI.
The thermal limiter cannot be reset and is not serviceable.
Control Actuators
Temperature Control Cable
The temperature control cable (19988) has the following features:
The cable assembly has a constant tension (pull-pull) dual cable design.
The pull-pull design allows for constant smooth communication between the temperature control
knob and the air temperature blend door.
The control cable can only be installed as an assembly.
Vacuum Control Motors
The vacuum control motors (18A318) control the position of the doors directing the air flow to the
different outlets. There are two types of vacuum control motors used in this system:
Single-diaphragm for air inlet and windshield defroster door operations.
Double-diaphragm for air damper door operations.
Single-diaphragm motors have two positions:
Shaft extended with no vacuum applied.
Shaft retracted with vacuum applied.
Double-diaphragm motors have three positions:
Shaft extended with no vacuum applied to either port.
Shaft halfway retracted with vacuum applied to only one port.