System Description

Fig.4 Heater-A/C Unit Housing:

MANUAL A/C (HVAC) / REAR WINDOW DEFOGGER
The Prowler comes standard with manual air conditioning. The system combines air conditioning, heating, and ventilating capabilities in a single unit housing mounted under the instrument panel. The actuators for Blend-Air And Fresh/Recirc are cable operated. The mode door is electrically activated by the BCM based on input from the HVAC control head. The BCM uses an electronic cycling switch to prevent evaporator freeze-up.

When the ignition is in the "RUN" position, the Body Control Module (BCM) monitors the electronic cycling switch state and the status of the A/C switch. Based on this information, the BCM sends a CCD message to the Powertrain Control Module (PCM) indicating the A/C switch status and the electronic cycling switch state.

The Body Control Module controls the mode door position by receiving different voltage levels from the HVAC control over the A/C mode switch MUX circuit. Included in this signal is the input for the rear window defogger. The Rear Window Defogger button is located in the center of the Mode Control knob. Press this button once to turn ON the Rear Window Defogger and a second time to turn it OFF. A LED in the button shows that the defogger is ON. The defogger turns OFF automatically after 10 minutes of operation. Each later activation will allow 5 minutes of operation. The timer functions for the rear window defogger are controlled by the BCM.

HEATING & AIR CONDITIONING

Fig.1 HVAC Controls:

System Airflow
The system draws outside air through the cowl opening at the base of the windshield. It then goes into the plenum chamber above the Heater A/C unit housing and passes through the evaporator. At this point, airflow can be directed either through or around the heater core. This is done by adjusting the blend-air door with the TEMP control on the control head. After the air passes the blend air door, the air flow is then directed from the PANEL, BI-LEVEL (panel and floor), and FLOOR-DEFROST outlets. Air flow velocity can be adjusted with the blower speed selector switch on the control head.

Ambient air intake can be shut off by rotating the RECIRC knob on the control head, closing the recirculating air door. This will recirculate the air that is already inside the vehicle. Rotating the MODE control knob to the Defrost/Floor or Defrost setting on the control head will engage the compressor. This will send refrigerant through the evaporator, and remove heat and humidity from the air before it goes through the heater core. The compressor can also be engaged by depressing the A/C button on the control head.