Heating and Air Conditioning: Description and Operation

The HVAC Programmer is the central component of the Electronic Air Conditioning and the Dual Zone Air Conditioning Systems . It receives inputs from the In-Vehicle Temperature Sensor, Solar Sensor, Ambient Temperature Sensor and driver selected temperature, mode, and Blower speed. In AUTO, the HVAC Programmer determines Blower speed and Air Mix Valve position. It also determines whether the Compressor will be engaged to reach the desired temperature.
When the system is in AUTO, air is discharged through the floor outlets when the vehicle is being warmed and through the panel outlets when the vehicle is being cooled.
The HVAC Programmer directs the flow of air to the proper outlets by controlling the operation of three Vacuum Actuators with four valve controls. When a valve control is energized, vacuum is applied to a Vacuum Actuator, causing a valve to move.
The Electronic Air Conditioning System Programmer controls an Air Mix Valve Actuator. The Air Mix Valve Actuator controls the Air Mix Valve, which directs air flow though the Heater Core or around it. The motor runs in forward or reverse direction by changing the polarity of the voltage applied to it. The HVAC Programmer uses the Air Mix Valve position feedback to calculate Air Mix Valve positioning.
The Dual Zone Air Conditioning System Programmer controls a Driver and a Passenger Air Mix Valve Actuator. These Actuators control the position of two Temperature Valves: one controlling the driver's side temperature; and one controlling the passenger's side temperature. Both Air Mix Valve Actuators employ bi-directional motors that are directed from forward to reverse by changing the polarity of the applied voltage.
The driver has two ways to control the HVAC Programmer. Mode, Blower speed, and temperature can be selected from the Heater and A/C Control Assembly. Temperature and Blower speed can also be selected from the Steering Wheel Controls (if equipped). These commands are transmitted to the HVAC Programmer via the E&C Data Line.