HVAC Temperature Controls Circuit Description (C68 & CJ2)

C68
The driver controls the temperature by engaging or disengaging the A/C compressor and directing the system air through or around the heater core. When the A/C compressor is not engaged, air flowing through the system may be heated above the outside air temperature. System air cannot be de-humidified or cooled below the outside air temperature.

When the A/C compressor is engaged, air flowing through the system is cooled, dehumidified and heated as needed.

This air treatment brings the vehicle interior to the desired temperature.

The heater and A/C programmer controls the A/C compressor operation from the network of sensor and the heater and A/C control.
^ Information from its network of sensors
^ The heater and A/C control

The programmer turns on the compressor if the following conditions are true:
^ The system is not turned OFF.
^ The outside temperature is above 8°C (48°F).
^ The programmer does not sense a low refrigerant level condition.

System air is then cooled and de-humidified.

The system air is heated, as needed, by passing the air through the heater core. An air mix valve is located inside the heater and A/C module assembly. This valve determines how much air passes around the heater core and how much air is forced through the core. When all of the air is forced through the heater core, maximum heating is obtained. When all of the air is routed around the heater core, no heating is obtained.

The air mix valve actuator operates the air mix valve. The actuator is mounted on the heater and A/C module assembly. The actuator contains a reversible CD motor. The CD motor is powered by the heater and A/C programmer. The programmer uses information from the heater and A/C control and its network of sensors. This information determines the appropriate air mix valve position. The programmer then powers the actuator motor. The motor runs in the direction that is necessary in order to move the air mix valve to the appropriate position.

CJ2
The driver controls the temperature by engaging or disengaging the A/C compressor and directing system air through or around the heater core.

In the dual zone system, the air mix door is split in half. Each half has its own actuator.

When the system is operating in dual zone mode, the heater and A/C programmer operates each actuator separately. The driver side discharge temperature depends on the following conditions:
^ The coolant temperature
^ The ambient air temperature
^ The inside air temperature
^ The left sun load sensor
^ The heater and A/C control temperature setting

The passenger side discharge air temperature depends on the following conditions:
^ The coolant temperature
^ The ambient air temperature
^ The inside air temperature
^ The right sun load sensor
^ The passenger climate control setting

When the system is not operating in dual zone mode, the actuators are operating in unison, as the system works in order to maintain the heater and A/C control temperature setting.