Operation
AUTOMATIC TEMPERATURE CONTROL (ATC)
Comfort temperature or perceived temperature is affected by air flow, sun levels on exposed skin, etc. The air temperature may be higher or lower than the comfort temperature. The automatic temperature control (ATC) system uses two infrared sensors in the instrument panel center stack to measure the temperature of the front occupants in order determine their comfort level relative to their selected comfort temperature. The integral HVAC computer adjusts temperature and air flow rates to maintain the customer-perceived comfort temperatures. The air temperature in the passenger compartment may be slightly higher or lower than the comfort temperature at any time. For instance, on sunny summer days the air flow will probably be cooler than the comfort temperature; on cold or cloudy days and at night it will probably be slightly warmer.
The Three-Zone ATC system uses the infrared sensors located in the instrument panel center stack along with an offset calibration strategy to meet the comfort requirements of the rear seat occupants.
FRONT CONTROL PANEL
- AUTO HI/LO - This system features two sets of automatic control logic that allow either a rapid cool-down rate or a somewhat slower cool-down rate with less fan noise. HI-AUTO controls the system to reach its assigned temperature quickly with a higher fan speed. LO-AUTO controls the system to reach its assigned temperature somewhat slower with less fan noise. Both modes will automatically engage auto recirculation.
- DEFROST - The defrost function must be manually selected to direct air flow to the windshield to remove fog or ice. The ATC system cannot automatically sense the presence of fog or ice on the windshield.
- RECIRC - The RECIRC button will close the air inlet door. If the system is in auto recirc (indicator being displayed automatically), pressing the manual recirc button will disable the auto recirc function until one of the auto keys are pressed or the ignition is cycled. If Auto HI/LO is pressed while manual recirc is active, manual recirc will be deactivated.
- REAR WINDOW DEFOGGER - Pushing the button sends a PCI bus message to the intelligent power module which controls the rear window defogger and side view mirror (if equipped) circuitry. The defogger function will be active for 10 minutes and can be turned off by a switch press. The defogger will function while the control is in the ON mode.
- FAN/MODE - The Fan and Mode knobs have 17 manual selectable positions. Manually changing either of the rotary knobs for mode or fan speed settings makes control of that blower motor manual. If only one is changed manually, the other remains under automatic control. Pressing the HI-AUTO/LO-AUTO rocker switch restores full automatic control.
- BLOWER DELAY TIMER - The word DELAY is displayed at start-up to signify that the system is waiting so that cold air will not be blowing. This tells the operator that it is unnecessary to turn the system off, raise the temperature setting or turn the fan speed setting down to prevent cold air from blowing. A countdown in minutes and seconds until the engine is warm enough to begin delivering heat to the passengers alternates with the DELAY message at 25 second intervals. This countdown is based on actual measurement of the rate of engine coolant temperature change. During the delay time, mix mode is selected and the fan operates at a low speed to keep the windshield fog free.
- REAR CONTROL (Three-Zone only) - When the Rear System control knob is moved to the OFF position, there will be a delay of approximately 1 second before the system actually turns off. This delay is to prevent an undesired blower dropout if the knob is moved through OFF to the other selections.
REAR CONTROL PANEL - THREE ZONE ATC SYSTEM
Primary control of the rear compartment heating-A/C system for the Three-Zone ATC system is in the instrument panel center stack. This control allows the driver to turn the rear heating-A/C system off, or allows the intermediate seat occupants control of the rear system by switching to the REAR position, or provides fully automatic control based on the temperature setting shown on the front control display.
- REAR CONTROL - Selecting automatic control of the rear unit at the instrument panel, illuminates a Locked Padlock in the rear control panel display. Selecting REAR activates the rear control panel and the Padlock then appears unlocked.
- FAN KNOB - The rear fan control has Off and AUTO positions and a range of manual speed settings that override the AUTO setting.
- MODE KNOB - The mode control allows intermediate seat occupants to manually override the automatic mode and select any balance of air flow between overhead and floor outlets from full overhead to full floor.
- SET TEMP - The rear set temp control will operate identical to the front controls. If the front control rear set temp button is pressed simultaneously with the rear control head, then the front control head press events shall have priority, i.e. if the front user presses Rear Set Temp down and the rear user presses Set Temp up, then the rear set temp will decrease.