Automatic Dual Zone With Rear Heat and A/C

AUTOMATIC DUAL ZONE WITH REAR HEAT AND A/C

The A/C-heater control (1) for the automatic temperature control (ATC) dual zone front heating-A/C system allows both the driver and the front seat passenger the ability to individually regulate air temperature for their side of the vehicle. Primary control for the rear heater-A/C system is also on the front A/C-heater control. An infrared sensor located in the overhead console detects thermal radiation emitted by the front seat occupants and their surroundings. All controls are identified by ISO graphic symbols.

FRONT CONTROL PANEL





The front A/C-heater control (1) and integral computer is located in the instrument panel and contains:

- a push button Auto mode control (2).
- Two rocker switch controls (3 and 11) to select both of the front and the rear comfort temperatures from 15° to 29° C (60° to 85° F). Comfort temperatures for each zone are shown in the vacuum-fluorescent (VF) digital display (4). If the set temperatures are 15° C (60° F) and down (-) is pressed, the A/C-heater control will attempt to achieve the lowest temperature possible, but the display will show LO. If the set temperatures are 29° C (85° F) and up (+) is pressed, the A/C-heater control will attempt to achieve the highest temperature possible, but the display will show HIGH. Temperatures can be displayed in either Metric or Fahrenheit, which is selected from the overhead console.
- a rotary control knob with integral push button control for front fan speed selection that can override the automatic controls and on/off control which allows the heating-A/C system to be completely turned off (5). The display is blank when the heater-A/C system is off, except for the ISO rear window defogger symbol when the rear window defogger system is on.
- a push button A/C on/off control (6). An ISO Snowflake symbol appears in the display when the A/C system is in operation, whether under manual or automatic control.
- a push button air recirculation control (7). A ISO Recirculation symbol appears in the display when the button is pressed, or when the system exceeds 80 percent circulated air under automatic control due to high A/C demand.
- five push button mode controls (8). An ISO mode symbol appears in the display to show the current mode setting when each button is manually pressed or selected by Auto mode.
- a push button rear window defogger on/off control (9). An ISO symbol appears in the display when the rear window defogger system is in operation. The ISO symbol will appear on the display even with the heating-A/C system turned off.
- a rotary control knob for rear window washer operation and rear window wiper speed selection (10).
- a push button control for rear heating-A/C system operation (12).
- two illumination lamps for backlighting of the controls (13).
- computer logic that remembers the settings of the controls when the ignition is turned off and retains those settings after a restart. If the system is off when the ignition is turned off it will be off when the engine is restarted, etc.
- computer logic that provides variable air recirculation under high temperature and humidity conditions. Because recirculation is generally accompanied by increased fan noise, the proportion of recirculated to outside air gradually approaches full recirculation over a broad temperature range.

The A/C-heater control for the ATC front dual zone heating-A/C system is diagnosed using a scan tool. Always run the calibration procedure to verify that the concern is not a system issue prior to replacing an A/C-heater control.

The front A/C-heater control cannot be repaired and must be replaced if found inoperative or damaged. The illumination lamps, rear wiper/wash control knob and the front fan speed/on/off control knob are available for service replacement.

The A/C-heater control utilizes integrated circuitry and information carried on the controller area network (CAN) B bus to monitor many sensors and switch inputs throughout the vehicle. In response to those inputs, the internal circuitry and programming of the A/C-heater control allows it to control electronic functions and features of the ATC heating-A/C system.

The inputs received by the A/C-heater control of the ATC heating-A/C system on the CAN B bus are as follows:

- Dimming
- Refrigerant Pressure
- Vehicle Identification Number
- Vehicle Odometer
- Engine Coolant Temperature
- Ambient Air Temperature
- Infrared Temperature Sensor
- Ignition Voltage
- Vehicle Speed

The messages broadcasted by the A/C-heater control of the ATC heating-A/C system on the CAN B bus are as follows:

- A/C Request
- A/C Select
- Rear Window Defogger (EBL) Request
- Rear Washer Request
- Rear Wiper Request

REAR CONTROL PANEL





The rear A/C-heater control (1) is located at the rear of the center floor console (2) and allows intermediate seat passengers to adjust rear temperature and blower motor speed when the control knob on the front A/C-heater control (3) is set to the Rear Manual position Description and Operation.