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:

- three rotary temperature controls (2) 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 (5). If the set temperatures are 15° C (60° F) and is adjusted lower, 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 is adjusted up, 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 rocker switch front fan speed control (3) that can override the Auto mode. A bar graph is shown in the VF digital display to indicate the selected or determined front fan speed (depending on manual or Auto mode).
- a push button front window defogger control (4). An indicator lamp illuminates in the control when selected manually and an ISO symbol appears in the VF digital display when selected by Auto mode.
- a push button air recirculation control (6). An indicator lamp illuminates in the control when selected manually and an ISO Recirculation symbol appears in the VF digital display when the system exceeds 80 percent circulated air under Auto mode due to high A/C demand.
- a rocker switch front mode control (7) that can override the Auto mode. An ISO mode symbol appears in the VF digital display to indicate the current mode setting when selected manually or by Auto mode.
- a push button A/C on/off control (8). An ISO Snowflake symbol appears in the VF digital display when the A/C system is in operation, whether under manual or Auto mode.
- a push button automatic mode control (9) to set the heating-A/C system to Auto mode. FRONT AUTO appears in the VF digital display when the system is in Auto mode.
- a rocker switch rear mode control (10) that can override the rear A/C-heater control and the Auto mode. An ISO mode symbol appears in the center portion of the VF display to show the current mode setting when selected manually or by Auto mode.
- two push button front heated seat controls (11). Each control has an indicator lamp that illuminates when selected.
- a push button control that locks out the rear heater-A/C controls (12), allowing only the driver and front seat passenger control of the rear heating-A/C system. An indicator lamp illuminates in the control when selected.
- a push button on/off control (13) that turns the rear heating-A/C system completely off. The center portion of the VF display is blank when the rear heating-A/C system is off.
- a push button rear window defogger on/off control (14). An indicator lamp illuminates in the control when selected. The indicator lamp illuminates in the control even with the heating-A/C system turned off.
- a rocker switch rear fan speed control (15) that can override the rear A/C-heater control and the Auto mode. A bar graph is shown in the center portion of the VF digital display to indicate the selected or determined rear fan speed (depending on manual or Auto mode).
- a push button synchronize control (16) that synchronizes the temperature of all three of the comfort zones to the drivers selected temperature. SYNC appears in the VF digital display when the system is synchronized, whether under manual or Auto mode.
- a push button on/off control (17) which allows the heating-A/C system to be completely turned off. The display is blank when the heater-A/C system is off.
- illumination lamps for backlighting of the control.
- 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 front A/C-heater control utilizes integrated circuitry and information carried on the controller area network (CAN) IHS 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 the 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 are as follows:

- Refrigerant Pressure
- Evaporator Temperature
- Engine Coolant Temperature
- Ambient Air Temperature
- Infrared Temperature Sensor
- Vehicle Speed

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

- A/C Request
- A/C Select
- Rear Window Defogger (EBL) Request
- Heated Front Seat Requests

The front A/C-heater control is diagnosed using a scan tool.

Prior to replacing an A/C-heater control, check for any diagnostic trouble codes (DTCs) related to the heating-A/C systems and run the calibration procedure to verify that the concern is not a system issueHVAC Actuator Calibration Procedure.

The front A/C-heater control cannot be repaired and must be replaced if inoperative or damaged.

REAR CONTROL PANEL






The rear A/C-heater control (1) is located in the rear overhead console and allows intermediate seat passengers to adjust rear air distribution, temperature and blower motor speed when the rear heating-A/C system primary on/off control in the front A/C-heater control in the instrument panel is set to the on position and the rear heater-A/C controls are NOT locked out by the driver and front seat passenger.

The rear A/C-heater control contains:

- a rotary control knob for fan speed selection and turning the rear heating-A/C system off or to Auto mode (2).
- a rotary control knob for temperature control of the rear discharged air (3).
- a rotary control knob for mode control of the rear discharged air (4).

The rear A/C-heater control is a slave potentiometer to the front A/C-heater control.
The rear A/C-heater control cannot be repaired and must be replaced if inoperative or damaged.