Control Assembly, HVAC

Control Assembly

The electronic automatic temperature control assembly is located in the instrument panel and consists of 10 push buttons, a variable blower speed knob for manual input. and a liquid crystal display (LCD) for displaying set temperature, ambient temperature and diagnostic codes.

There are five light Emitting Diodes (LEDs) to display the manual mode overrides and two LED light bars to indicate automatic function and automatic fan control. The set temperature can be raised or lowered in one degree increments between 18 and 29C (65 and 85F) through the use of a warmer or cooler (blue) button. There is also a 16C (60F) setting for maximum cool and a 32C (90F) setting for maximum heat When the outside button is pressed, the LCD will display the outside ambient temperature for four seconds and then return to the set temperature display. The remaining six buttons select a manual function override: off,A/C, defrost, floor, panel, and recirc.

Whenever the blower knob is turned, the automatic blower control is overridden, and a manual blower speed is selected. When the parking lamps/headlamps are activated, the LCD will dim, the bezel backlighting will turn on, and the LEDs will dim. As the rheostat voltage is varied, the LCD and backllghting intensity will vary. whenever the miles/km button on the vehicle's cluster button assembly is pressed (vehicles equipped with an electronic cluster only), the temperature setting will be displayed in degrees Fahrenheit (F). The display will change to a degrees Celsius (C) indication when the cluster button assembly miles/km button is pressed again.

The control assembly performs the following functions:
- Processes data from the manual inputs to the control panel; from in-vehicle, ambient, engine temperature and sunload sensor, and from the blend door actuator position sensor.
- When the ignition switch is turned to the RUN position, the control will remember the last temperature, function and blower setting
- Provides continuous position control of ~e blend door actuator.
- Provides discrete, two-position control of the panel- defrost and outside-recirc vacuum actuator.
- Provides three-position control of the function actuator.
- Provides a continuously variable blower signal which is amplified by the solid-state blower speed control (BSC) module ad the high blower relay (HBR) to control the blower voltage.
- Provides an A/C power feed which is delivered to the pressure switch by a relay built into the control.