A/C-Heater System

Depending on vehicle, a dual-zone or 3-zone Heating, Ventilation, Air Conditioning (HVAC) system is available. The A/C-Heater Control Module performs the following:

• Is fully addressable with the DRBIII(R).
• Communicates over the PCI Bus.
• Uses input from the Evaporator Temperature Sensor to prevent evaporator freeze up while maintaining optimum cooling performance.
• Provides an A/C request to the PCM over the PCI Bus when compressor operation is desired.
• Controls Blower Motor operation, providing 4 blower speeds.
• Controls Heated Mirror and Electric Back Light (EBL)/Rear Window Defogger operation (if equipped).
• Controls Rear Washer Pump operation.
• On 3-zone systems, activates and deactivates the Rear A/C Control.
• On 3-zone systems, controls rear blower operation, providing 3 blower speeds.
• On 3-zone systems, controls rear heater coolant pump operation.
• Controls operation of the front and 3-zone system rear electronic Door Actuators.

The Rear A/C-Heater Control Module on 3-zone system performs the following:

• Controls Rear Blower Motor operation, providing 3 blower speeds.
• Provides desired Rear Blend and Mode Door position input to the A/C-Heater Control Module.

The Dual-Zone HVAC system uses:

• Two, 2-wire electronic Blend Door Actuators.
• One, 2-wire electronic Mode Door Actuator.
• One, 2-wire electronic Recirculation Door Actuator.

The 3-Zone HVAC system uses:

• Two front, 2-wire electronic Blend Door Actuators.
• One front, 2-wire electronic Mode Door Actuator.
• One, 2-wire electronic Recirculation Door Actuator.
• Two rear, 2-wire electronic Blend Door Actuators.
• One rear, 2-wire electronic Mode Door Actuator.

A simplified control system for operation of the mode, recirculation, and temperature control actuators provides positive positioning without the complexity of feedback from position sensors. The A/C-Heater Control Module knows the number of operating actuator revolutions required for full door travel as well as the number of actuator commutator pulses per revolution. Using these parameters, the A/C-Heater Control Module runs the actuator for the number of commutator pulses that correspond to the desired door position. To maintain accuracy, the system recalibrates itself periodically at known zero and full travel conditions. For additional information on A/C-Heater System, see MANUAL A/C-HEATER SYSTEMS - DAKOTA & DURANGO article in AIR CONDITIONING & HEATING.