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Automatic Three Zone






AUTOMATIC THREE ZONE - LHD

The Automatic Temperature Control (ATC) three zone heating-A/C system allows the driver and the front and rear seat passengers the ability to automatically or manually regulate air temperature for their individual zones. Primary control for the rear heater-A/C system is on the front A/C-heater control. All controls are identified by International Standardization Organization (ISO) graphic symbols.

FRONT CONTROL PANEL





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

- a push button A/C on/off control (2). An ISO Snowflake symbol appears in the Vacuum-Flourescent (VF) digital display (3) when the A/C system is in operation, whether under 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.
- four push button temperature controls (5 and 18) to select the front comfort temperatures from 15° to 31° C (60° to 88° F). 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 31° C (88° 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 push button rear heating-A/C system on/off control (6). ISO symbols appear in the VF digital display to indicated when the rear system is off or on, whether under manual or Auto mode.
- a push button rear window defogger on/off control (7). 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 Heated Glass - Operation.
- a push button control that locks out the rear heater-A/C controls (8), 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 automatic mode control (9) to set the heating-A/C system to Auto mode. AUTO appears in the VF digital display when the system is in Auto mode.
- two push button front heated seat controls (10 and 13). Each control has two indicator lamps that illuminate, depending on seat temperature selected Heated Seats - Operation.
- a rotary control knob for fan speed selection and turning the heating-A/C system off (11).
- a cab temperature sensor (12) is located in the center of the A/C-heater control. The sensor detects thermal radiation emitted by the front seat occupants and their surroundings.
- a push button mode control (14) to 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. Auto mode provides variable air recirculation through a broad range of high temperature and humidity conditions.
- a push button heated steering wheel switch (15). when equipped. An indicator lamp illuminates in the control when selected manually or automatically with remote start mode.
- a push button air recirculation control (16). The Recirculation button contains an LED that illuminates when the recirculation function is manually activated. The ATC A/C-heater control computer logic provides variable air recirculation through a broad range of temperature and humidity conditions.
- a push button synchronize control (17) that automatically adjusts the temperature of the front passenger comfort zone to the drivers comfort zone temperature. An LED illuminates in the SYNC button when the SYNC function is manually activated. SYNC appears in the VF digital display when the system is synchronized, whether under manual or Auto mode.
- illumination lamps for backlighting of the ATC A/C-heater 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.

The front ATC A/C-heater control utilizes integrated circuitry and information carried on the Controller Area Network (CAN) bus to monitor many sensors and switch inputs throughout the vehicle. In response to these inputs, the internal circuitry and programming of the ATC A/C-heater control allow it to control electronic functions and features of the ATC heating-A/C system.

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

- A/C Clutch Engage
- Ambient Air Temperature
- A/C-heater control backlight dimming
- Engine Coolant Temperature
- Engine Speed
- Refrigerant Pressure
- Electrical System Voltage
- Vehicle Identification Number
- Vehicle Odometer
- Vehicle Speed

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

- A/C Request
- EBL Status
- Heated Seat Select
- Heated Steering Wheel Select

The front A/C-heater control for the ATC three zone heating-A/C system 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 system and initiate the Actuator Calibration function to verify that the concern is not a heating-A/C system calibration issue HVAC System Test.

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

REAR CONTROL PANEL





The rear ATC A/C-heater control (1) is located in the rear overhead console (6) or headliner, depending on trim level. The rear ATC A/C-heater control 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 is a slave potentiometer to the front A/C-heater control.

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).
- an red indicator lamp that illuminates when the rear A/C-heater controls are "locked out" by the front A/C-heater control (5).

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

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