HVAC Programmer

The heater and A/C programmer contains a micro-processor and is the brain of the electronic or dual zone system. The programmer receives electrical signals from the heater and A/C control, passenger climate control, right and left sun load sensors, ambient air temperature sensor, inside air temperature sensor, blower control module, powertrain control module, driver and passenger air mix valve actuators.

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 heater and A/C programmer. There are four of these valves and each controls vacuum to a different vacuum actuator. By energizing various combinations of these solenoid actuated vacuum valves, the heater and A/C 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 heater and A/C programmer also performs self-diagnosis functions for the electronic or dual zone system. The microprocessor identifies faults when the system is operating and stores this information in memory. When the system diagnostic mode is activated through the use of a scan tool, these faults are displayed as numeric diagnostic trouble codes (DTCs).