Front - Manual Temperature Control (MTC) Tri Zone
MANUAL TEMPERATURE CONTROL (MTC) TRI ZONE
The A/C-heater controls for the Manual Temperature Control (MTC) tri-zone heating-A/C system allows the driver, front seat passenger and the intermediate seat passengers, the ability to individually regulate air temperature as well as fan speed for their portion of the vehicle. Primary controls for the rear heating-A/C system are located on the front A/C-heater control panel. All controls are identified by ISO graphic symbols.
FRONT CONTROL PANEL
The front MTC dual zone A/C-heater control and integral computer (1) is located in the instrument panel and contains:
- three rotary temperature controls (2, 7 and 9) to select the separate temperatures for both of the front comfort zones and the rear comfort zone
- five push button mode controls (3 and 5) to select the position of the discharged air for the driver and front passenger comfort zones. An indicator lamp illuminates in each of the controls when selected.
- a rotary control knob for front fan speed selection and turning the heater-A/C system off (4).
- a push button air recirculation control (6). An indicator lamp illuminates in the control when selected.
- a push button rear window defogger on/off control (8). An indicator lamp illuminates in the control when selected. The rear window defogger system operates and the indicator lamp illuminates in the control even when the heating-A/C system is turned off.
- a rotary control knob for rear fan speed selection and turning the rear heater-A/C system off (10). This control has a position for locking out the rear heater-A/C controls, allowing only the driver and front seat passenger control of the rear heating-A/C system.
- a push button A/C on/off control (11). An indicator lamp illuminates in the control when the A/C system is in operation.
- computer logic that remembers the settings of the A/C-heater control 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.
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 MTC heating-A/C system.
The front A/C-heater control is diagnosed using a scan tool Testing and Inspection.
Prior to replacing an A/C-heater control, check for any Diagnostic Trouble C 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 front A/C-heater control cannot be adjusted or repaired and must be replaced if inoperative or damaged.
REAR CONTROL PANEL
The rear MTC A/C-heater control is located in the headliner 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 or front seat passenger.
The rear A/C-heater control (1) contains:
- a rotary control knob for fan speed selection and turning the rear heating-A/C system on and off (2).
- a rotary control knob for temperature control of the rear discharged air (3). An indicator lamp illuminates in the control when the rear heater-A/C controls are locked out by the driver or front seat passenger.
- 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 and cannot be adjusted or repaired and must be replaced if inoperative or damaged.