DESCRIPTION
| WARNING | To avoid injury from accidental air bag deployment, read and carefully follow all SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM procedures in AIR BAG SYSTEM SAFETY article in GENERAL SERVICING. |
| CAUTION | When battery is disconnected, radio will go into anti-theft protection mode. Obtain radio anti-theft protection code from owner prior to servicing vehicle. |
Automatic A/C system is controlled by the Automatic Temperature Control Electronic Control Unit (ATC ECU). While A/C system is on, ATC ECU operates refrigerant system and inlet air, blower speed, air temperature and air distribution functions to produce conditions requested on control panel. When A/C system is first turned on, ATC ECU resumes control outputs in use when A/C system was last turned off. If conditions have changed, or a different mode is selected to turn A/C system on, control outputs are then changed to produce required new settings. Automatic modes provide optimum control of system under most conditions and require no manual intervention. Manual modes allow individual functions of automatic operation to be overridden, to accommodate personal preferences. A/C system consists of a refrigerant system, a heater assembly and a control system. (Scheme 5)and (Scheme 6).
A/C system operates in automatic, economy and defrost modes, with manual overrides of inlet air source, blower speed and air distribution. Air temperature is automatically controlled in all operating modes. In automatic mode, ATC ECU operates A/C system to warm-up or cool down cabin to establish and maintain selected temperatures on control panel, while directing air to those outlets most comfortable for the occupant(s). If different temperature selections between driver's side and passenger's side cause a conflict of required inlet air source, blower speed or air distribution settings, priority is given to achieving temperature requested on driver's side of control panel.
ATC ECU enters economy mode when refrigerant compressor is selected off while system is in automatic mode. Economy mode operation is similar to automatic mode, but without the ability to cool the cabin if ambient temperature is more than temperature selections made on control panel, or to dehumidify air in the cabin. In defrost mode, ATC ECU sets inlet air source to fresh air, blower to maximum speed, air distribution to windshield and side windows, and outputs signals to Body Control Unit (BCU) to operate rear window heater and windshield heater (if equipped). BCU starts or, if heaters are already operating, resets heater timers and energizes rear window and windshield heaters for a complete operation cycle.
On vehicles equipped with rear A/C, additional cooling is provided by recirculating air through a second evaporator and distributing it to outlets in roof. Rear A/C system consists of 2 refrigerant lines, a rear evaporator/blower assembly, a distribution system and a control panel. Cooled air from rear evaporator/blower assembly is supplied by the distribution system to vent outlets above each second and third row seat. Rear A/C system is controlled by 2 switches on rear control panel. A variable speed blower and/or ram air effect, forces air through rear system. Depending on control panel settings, air is then heated and supplied through distribution ducts to instrument panel and floor level outlets.
