Rear Passenger Face Level Air (Automatic System Only)

Rear Passenger Face Level Air (Automatic System Only)

The volume and temperature of the air from the rear passenger face register are adjusted with the thumbwheels at the sides of the register. Each thumbwheel operates a variable potentiometer connected to the ATC (automatic temperature control) module. The volume thumbwheel controls stepless changes of rear blower speed between off and full speed. The temperature thumbwheel controls the position of the rear passenger face level blend door in the heater assembly when the driver's side reference temperature is more than 0%.

Volume Control
The volume potentiometer outputs between 0 and 5 V to the ATC (automatic temperature control) module. The ATC (automatic temperature control) module translates the voltage from the potentiometer into a signal voltage for the output stage in the rear blower. Potentiometer voltages of less than 1.25 V are interpreted as a blower off selection and translate into a signal voltages less than 0.1 V. Potentiometer voltages between 1.25 and 5 V are translated into proportional signal voltages between 0.1 and 5 V.

The ATC (automatic temperature control) module automatically switches off the rear blower when:
^ The defrost program is active.
^ The main blower is selected off.
^ The engine cranks.
^ The ignition is selected off (the rear blower remains off during rest heating, parked heating and parked ventilation).

Temperature Control
The temperature potentiometer outputs between 0 and 5 V to the ATC (automatic temperature control) module. The ATC (automatic temperature control) module translates the voltage from the potentiometer into a blend door position between 0% (cold) and 100% (hot) and outputs the appropriate control signal on the M bus to the blend door motor. Potentiometer voltages of less than 1.5 V translate to a blend door position of 0%. Potentiometer voltages of more than 3.4 V translate to a blend door position of 100%. Potentiometer voltages between 1.5 and 3.4 V translate linearly to blend door positions between 0 and 100%.