Control Assembly: Description and Operation
Climate Control Panel Operation
The Control Panel contains: Fan speed/defrost rotary switch, Heated front screen button, Demist mode button, Temperature differential slider, Temperature rotary control, On, Max, Manual, and Recirculation mode buttons. The control panel relays information to the electronic control module.
The FAN SPEED CONTROL rotary switch controls airflow from the blower motors. The switch has five positions: OFF, LOW, MED, HIGH and DEFROST In the OFF position the system is not operational, how- ever, a residual signal to the control module (Al CCM) ensures that the blower flaps are closed, thus preventing outside air from entering the system. Information regarding selection by the control switch of LOW, NORM and HIGH fan speeds is relayed to the Al CCM. Signals are also relayed to the Al CCM from the temperature selector feedback circuits and various sensors. Fan speed is steplessly controlled by the Al CCM, within the ranges MED and LOW. When DEFROST is selected the fans operate at maximum speed, front screen vents open fully, lower flaps close fully and maximum output is directed to the windscreen (there may be a delay of up to 30 seconds from selection to execution of this function).
HEATED FRONT SCREEN where fitted, allows rapid screen deicing using laminated electrical heating elements to supplement the normal hot air defrost mode. The elements are automatically energized when Defrost is selected and are timed to switch off after approximately six minutes of continuous use. However, the screen heater may be manually switched on or off at any time.
The DEMIST mode button, when pressed, causes increased air flow to the front screen.
The FACE LEVEL TEMPERATURE DIFFERENTIAL sliding control is used to vary the temperature of the face vent distributed air to that of the footwell delivered air.
The TEMPERATURE ROTARY CONTROL is used to preset the in car heat level in either "automatic or manual" mode. There are two temperature sensors located in the system, exterior ambient, and in-car sensors.
An input voltage is supplied to the sensors from AC4-13 of the control module. The temperature sensing signal from the sensors is transmitted to the control module via AC4-4 and AC2-4 respectively. The sensors are semi-conductor devices which provide a voltage output proportional to the sensed temperature.
When pressed, the ON button, causes the system to engage the air conditioning compressor via its electro-magnetic clutch.
The MAX mode, when selected, provides full air conditioning performance by setting the system to high fan speed and full cooling. This may be cancelled by further operation of the MAX button or by pressing the ON button.
When engaged, with indicator lamp lit, the MANUAL MODE facility provides operator selection of fan speed and in car temperature. In car temperature will not be thermostatically corrected to a predetermined level via the system sensors.
Automatic temperature control is resumed when the button is pressed and the indicator lamp is unlit.
RECIRCULATION mode closes the blower flaps and circulates only that air which is in the vehicle. When the ignition is turned off the blower flaps revert to the fresh air position.