Automatic Zone Control (AZC) Module

The Automatic Zone Control (AZC) Module:

• Is fully addressable with the DRBIII(R).
• Communicates over the Programmable Communication Interface (PCI) Multiplex System Bus.
• Has dual infrared sensors, mounted in the AZC module face, which independently measure surface temperature to maintain occupant comfort levels.
• Has dual-zone temperature controls to provide a wide side-to-side variation in temperature to meet the needs of either front seat occupant.
• Can be operated in a manual mode.
• Uses engine temperature data, received over the PCI Bus, for cold engine blower lock-out.
• Uses engine RPM data, received over the PCI Bus, for wide-open throttle A/C cut-out.
• Uses vehicle speed data, received over the PCI Bus, to determine airflow over the condenser for optimum cooling performance.
• Uses evaporator temperature sensor data, received over the PCI Bus, to prevent evaporator freeze up while maintaining optimum cooling performance.
• Uses ambient temperature sensor data, received over the PCI Bus, to optimize comfort control.
• Provides an A/C request to the BCM when compressor operation is desired.
• Controls rear defogger operation.
• Controls fan speed, providing 10 blower speeds in manual mode and infinite speeds in automatic mode.
• Controls electronic door actuator operation.

The Blower Motor Controller provides a 5-volt signal to the AZC Module over the blower motor control circuit. The AZC Module provides a variable duty cycle ground to the 5-volt signal, based on input from the blower switch. When the blower switch is set to LO speed, the AZC Module provides a short duty cycle (less time grounding the signal voltage). As higher blower speeds are requested, the AZC Module increases the duty cycle (more time grounding the signal voltage). When the blower switch reaches HI speed, the duty cycle increases to where the signal pattern is almost a flat line (with brief voltage spikes).

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 AZC 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 AZC 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. See AUTOMATIC A/C-HEATER SYSTEMS - GRAND CHEROKEE article in HVAC for additional AZC system description and operation information.

The Dual-Zone AZC HVAC system uses 2 two-wire electronic blend door actuators, a two-wire electronic mode door actuator and a two-wire electronic recirculation door actuator.