Heater and A/C Programmer

DESCRIPTION

The Heating Ventilation and Air Conditioning (HVAC) programmer contains a micro-processor and is the "brain" of the electronic A/C system.

OPERATION

The programmer receives electrical signals from the heater and A/C control assembly, solar sensor, ambient temperature sensor, in-vehicle temperature sensor, blower control module, powertrain control module and air mix valve actuator. A microprocessor in the programmer processes the signals and then sends commands to the system components which control A/C compressor clutch operation, air intake location, air discharge location, air discharge temperature and blower speed.

The solenoid actuated vacuum valves that control air intake and discharge locations are located inside the HVAC programmer. There are four of these valves and each controls vacuum to a different vacuum chamber. 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 defroster outlets, and whether fresh (outside) air is drawn into the system or inside air is recirculated.

The HVAC programmer also performs self-diagnosis functions for the electronic A/C 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 Vacuum Florescent (VF) display.