System Controls

The A/C-Heater Control Module:

• is fully addressable with the DRBIII(R).
• communicates over the Programmable Communication Interface Multiplex System (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 Powertrain Control Module (PCM) over the PCI Bus when compressor operation is desired.
• controls front blower motor operation, providing four blower speeds (Low, Ml, M2 & High).
• controls heated mirror and EBL operation.
• controls rear washer pump operation.
• on three-zone systems, activates and deactivates the Rear A/C-Heater Control.
• on three-zone systems, controls rear blower motor operation, providing three blower speeds (Low, Med, & High).
• on three-zone systems, controls rear heater coolant pump operation.
  1. To assist the HVAC system in maintaining a consistent and optimum heat output at low vehicle speeds, an electric coolant pump operates under specific conditions to keep a steady flow of hot coolant circulating through the heater circuit. The pump runs when all of the following conditions are met: When the vehicle's speed is below 27 Km/h (17 mph), the coolant temperature is between 65.5°C and 110°C (150°F and 230°F), the front blower is turned on, and the blend control is set above 60% reheat. The A/C - Heater Control Module turns the pump off if any one of the following conditions occur: The vehicle speed rises above 48.3 Km/h (30 mph). The coolant temperature drops below 65.5°C (150°F). The coolant temperature rises above 110°C (230°F). The front blower is switched off. The blend control is set below 60% reheat.
• controls the front and three-zone system rear electronic door actuators' operation.
  1. 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.

On Three-Zone systems, the Rear A/C-Heater Control:

• controls rear blower motor operation, providing three blower speeds (Low, Med, & High).
• provides desired rear blend and mode door position input to the A/C-Heater Control Module.

The Dual-Zone HVAC system uses:

• two, two-wire electronic blend door actuators.
• one, two-wire electronic mode door actuator.
• one, two-wire electronic recirculation door actuator.

The Three-Zone HVAC system uses:

• two front, two-wire electronic blend door actuators.
• one front, two-wire electronic mode door actuator.
• one, two-wire electronic recirculation door actuator.
• one rear, two-wire electronic blend door actuator.
• one rear, two-wire electronic mode door actuator.