Front - Automatic Temperature Control (ATC) Dual Zone

AUTOMATIC TEMPERATURE CONTROL (ATC) DUAL ZONE

The A/C-heater control 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. An infrared sensor located in the overhead console detects thermal radiation emitted by the front seat occupants and their surroundings. Based on the sensor input, the system automatically adjusts the air temperature, airflow volume, airflow distribution and amount of inside air recirculation to maintain front seat occupant comfort, even under changing outside weather conditions. All controls are identified by ISO graphic symbols.

The ATC dual zone heating-A/C system uses a dedicated microprocessor to automatically drive the electrically operated door actuators. The ATC A/C-heater control obtains vehicle speed, engine speed, engine coolant temperature, ambient temperature and refrigerant system pressure. The ATC A/C-heater control communicates with other electrical modules in the vehicle over the Controller Area Network (CAN) IHC bus.

This ATC system provides the vehicle operator with a number of setting options to help control the climate and comfort within the vehicle and offers several manual override features such as fan speed, airflow distribution, defrost mode and when the outside air contains smoke, odors or high humidity, the interior air can be manually recirculated.





The ATC dual zone A/C-heater control (1) is located in the instrument panel and contains:

- a push button on/off control which allows the heating-A/C system to be completely turned off (2). The Vacuum-Fluorescent (VF) digital display (4) is blank when the heater-A/C system is off.
- two rotary temperature controls to select both driver and front seat passenger comfort temperatures from 15° to 29° C (60° to 85° F) (3 and 5). Comfort temperatures for each zone are shown in the VF digital display. 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.
- a push button A/C on/off control (6). 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 air recirculation control to set the heating-A/C system to Recirculation mode (7). An ISO Recirculation symbol appears in the VF digital display when Recirculation mode is selected and when the system exceeds 80 percent circulated air under Auto mode (due to high A/C demand).
- a rocker switch mode control that can override the Auto mode (8). 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 rear window defogger on/off control (9). 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 push button front window defogger control (10). 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 rocker switch fan speed control that can override the auto mode (11). 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 automatic mode control to set the heating-A/C system to auto mode (12). AUTO appears in the VF digital display when the system is in auto mode.
- 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 heating-A/C system is off when the ignition is turned off, the system will be off when the engine is restarted.
- 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 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

The A/C-heater control for the ATC heating and A/C system is diagnosed using a scan toolTesting and Inspection.

Prior to replacing an A/C-heater control, check for any Diagnostic Trouble Codes (DTCs) related to the heating-A/C system, and run the calibration procedure to verify that the concern is not an air-door calibration issue HVAC System Test.

The A/C-heater control cannot be adjusted or repaired and must be replaced if inoperative or damaged. The illumination lamps for the A/C-heater control can be serviced separately.