Programmer

DESCRIPTION

The Programmer converts electrical signals from the heater and A/C control assembly into vacuum commands which position the temperature valve, A/C defrost valve and 0/S air-recirc. valve; all located in the air distributor assembly.

OPERATION

Vacuum is constantly applied to a programmer check valve which distributes the vacuum to four solenoid-controlled valves. When the heater and A/C control assembly signals the programmer to change an air distributor valve, the associated solenoid is energized and vacuum is applied to a vacuum actuator. The actuator, in turn, repositions its air distributor valve.

The programmer contains a microprocessor which receives signal information from sources such as the control panel switches, temperature sensors, and the temperature valve feedback potentiometer in the programmer. In turn, the microprocessor sends command signals to position the air valves. The microprocessor also sends signals to the blower motor control module to control the blower speed. This enables the system to maintain a set in-vehicle temperature of 16°C (60°F) to 32°C (90°F).

The microprocessor retains the operating mode, blower mode, and temperature settings when the ignition is turned off. The microprocessor resets to the "AUTO" mode after a reset condition (loss of battery power) occurs.

An additional function of the microprocessor is that of system self-diagnosis. Faults in the temperature sensor circuits and temperature valve control circuit are identified when the heater and A/C control assembly is set to the diagnostic mode. Diagnostic codes are displayed on the control assembly Vacuum Florescent (VF) display. If the system does not have an identifiable fault, a OO code is displayed. For diagnostic mode activation and fault code identification, Refer to Air Door Actuator / Testing and Inspection. Testing and Inspection

The programmer also operates a bi-directional DC motor, which is controlled by signals from the heater and A/C control assembly as well as information from the in-vehicle and outside air temperature sensors, the solar sensor and the set temperature.

As the temperature valve actuator motor turns, it moves a plastic crank arm, which in turn moves a threaded, adjustable link rod connected to the temperature valve to obtain the correct blend of heated air from the heater and cooled air from the A/C evaporator.