Dual Zone Climate Controls

System Block Diagram:

GENERAL INFORMATION
The dual air conditioning system (CJ2) is an electronically controlled heating, ventilating and air conditioning system that automatically maintains a selected temperature for the passenger compartment, regardless of outside temperature changes. The system includes a passenger side climate control assembly which allows the front seat passenger to increase or decrease air discharge temperature on that side of the vehicle. The system also has self-diagnostic capabilities.

The system uses a cycling clutch orifice tube (CCOT) type refrigeration system.

SYSTEM COMPONENTS

Heater and A/C Control Assembly
The heater and A/C control assembly allows the vehicle operator to communicate with the system. The heater and A/C control assembly includes soft-touch buttons for the various system operating modes (OFF, AUTO, DUAL ZONE, HEATER, ECONOMY, DEFOG, DEFROST), fan speed control (AUTO, LO, HI), temperature control (COOL, WARM), rear window defogger and outside air temperature display. Each operating mode button (except OFF) contains an LED Indicator which illuminates when that mode is selected. The rear window defogger button also contains an LED Indicator.

The heater and A/C control assembly includes a Vacuum-Fluorescent (VF) display which shows the set temperature, outside air temperature (when selected), a fan speed indicator and mode indicators for OFF and AUTO. During self-diagnosis, the VF display shows diagnostic trouble codes which can identify faults within the system.

Passenger Climate Control Assembly
The passenger climate control assembly includes 2 soft-touch buttons and a bar segment display. The soft-touch buttons (COOL, WARM) are used to raise or lower passenger side outlet air temperature. The bar segment display is made up of 9 LEDs (4 green, 1 amber, 4 red) and indicates passenger-side outlet air temperature relative to driver-side outlet temperature. The passenger climate control assembly is activated only when the system is operating in the DUAL ZONE mode.

HVAC Programmer
The HVAC programmer is the brain of the dual air conditioning system. The programmer receives electrical signals from the heater and A/C control assembly, passenger climate control assembly, RH solar sensor, LH solar sensor, ambient temperature sensor, in-vehicle temperature sensor, blower control module, powertrain control module (PCM), driver air mix valve actuator and passenger air mix valve actuator. A microprocessor in the programmer processes these signals and then sends commands to the system components that control A/C compressor operation, air discharge location, air discharge temperatures (driver and passenger sides) and blower speed.

The solenoid-actuated vacuum valves, which control air discharge location. are located inside the HVAC programmer. There are four valves; each controls vacuum to a separate vacuum diaphragm. By energizing various combinations of these solenoid-actuated vacuum valves, the HVAC programmer can control whether air comes out the floor outlets, panel outlets, or windshield outlets and whether fresh (outside) air is drawn into the system or inside air is recirculated.

The HVAC programmer microprocessor also performs self-diagnostic functions for the system. The microprocessor identifies faults in the temperature sensor, solar sensor and air mix valve actuator circuits when the system is operating and stores this information in memory. Then, when the system diagnostic mode is activated, these faults are displayed as numeric diagnostic trouble codes on the heater and A/C control assembly VF display.

Heater And A/C Module
The heater and A/C module is the unit in which all system air is heated, cooled, mixed together, and directed to the various air ducts and outlets. The module consists of a housing with inlet openings, outlet openings, air passages and air valves. Vacuum actuators and electric motors mounted on the housing operate the air valves, following signals provided by the HVAC programmer.

In-Vehicle Temperature Sensor
The In-vehicle temperature sensor is a temperature-sensitive resistor whose resistance varies inversely with temperature; as in-vehicle air temperature increases, resistance decreases and, as in-vehicle air temperature decreases, resistance increases. The HVAC programmer monitors the in-vehicle temperature signal and uses it to help determine command signals.

A hose duct connects the in-vehicle temperature sensor housing to an aspirator; air flow through the heater and A/C module creates a slight vacuum at the aspirator end of the hose. This vacuum draws in-vehicle air over the sensor, improving the accuracy of the in-vehicle temperature reading.

Ambient Temperature Sensor
The ambient temperature sensor is a temperature-sensitive resistor like the in-vehicle temperature sensor. As outside air temperature increases, resistance decreases; as outside air temperature decreases, resistance increases. The HVAC programmer monitors the ambient temperature signal and uses it to display outside air temperature on the heater and A/C control assembly and to help determine command signals.

LH Solar Sensor
The LH solar sensor is a light-sensitive photo diode used to determine the sun's heat load on the vehicle's driver side. The HVAC programmer compares the solar value to the in-vehicle temperature and determines how much cooling is required to reach and maintain the selected passenger compartment temperature.

RH Solar Sensor
The RH solar sensor is identical to the LH solar sensor, but is used to determine the sun's heat load on the vehicle's passenger side. The HVAC programmer uses input from the RH solar sensor to help determine passenger side outlet air temperature when the system is operating In the DUAL ZONE mode.

Blower Control Module
The blower control module is a solid-state device that operates the blower motor. The blower control module outputs a voltage that varies between 0 volts (blower motor OFF) and 12 volts (maximum blower motor speed).

To determine the appropriate output voltage, the blower control module monitors a varying voltage signal (between 2 and 8 volts) from the HVAC programmer. The module then amplifies the signal and applies voltage directly to the blower motor. Blower control module voltage is also monitored by the HVAC programmer.

Blower Motor
The blower motor is a DC motor whose speed is proportional to input voltage. With low voltage applied to the motor, it runs at low speed; with high voltage applied to the motor, it runs at high speed. The blower control module applies voltage to the blower motor, following commands from the HVAC programmer.

Driver Air Mix Valve Actuator
The driver air mix valve actuator controls driver side outlet air temperature, following commands from the HVAC programmer. A reversible DC motor in the actuator operates the driver air mix valve, which blends cooled and heated air inside the heater and A/C module. The driver air mix valve actuator contains a feedback potentiometer, which informs the HVAC programmer of driver air mix valve position.

Passenger Air Mix Valve Actuator
The passenger air mix valve actuator operates in the same way as the driver air mix valve actuator, but it controls passenger side outlet air temperature by operating the passenger air mix valve. Like the driver air mix valve actuator, it also contains a feedback potentiometer, which informs the HVAC programmer of its air mix valve position.

Vacuum Actuators
The vacuum actuators are vacuum servos used to operate valves inside the heater and A/C module. Valve position determines whether air comes out the floor outlets, panel outlets or windshield outlets and whether fresh (outside) air is drawn into the system or inside air is recirculated. Three actuators are used: two single-diaphragm actuators and one double-diaphragm actuator. The vacuum actuators are mounted on the heater and A/C module and are connected to the HVAC programmer by vacuum hoses.