For 1990-2009 cars

### Controller

The operation of the A/C system is controlled by the switches on the control head. This console-mounted heating and ventilation system consists of control knobs and a vacuum fluorescent display (VFD) indicating the status of the control settings selected.

#### Temperature Control Push Knobs

• | Raise the temperature of the air entering the vehicle by turning the rotary switch clockwise (red arrow direction).

• | Lower the temperature of the air entering the vehicle by turning the switch counterclockwise (blue arrow direction).

• | Actuate the air mix door by an electric motor.

• | Vary the mix of the air passing through the heater core with the air bypassing the core.

• | Each press of a switch changes the set temperature by increments of 0.5°C (1°F). This is shown in the temperature window on the function display.

#### Vacuum Fluorescent Display (VFD)

• | Temperature setting--Indicates the temperature set with temperature control knob.

• | Auto status--Indicated whether the system is operating in the full automatic mode or manual mode.

• | Defroster icon--Indicates manual selection of full defrost mode.

• | Mode--Indicated by icon, the mode chosen by the system in auto (or by the operator in manual) is shown by an illumination arrow indicating the air path.

• | A/C--A snowflake icon indicating whether the A/C is ON or OFF.

• | Fan speed--Indicates the fan speed by illuminating a bar based on the segment at the front, for low speed, and adding additional segments in order up to the eighth, for high speed.

#### Seven Additional Push Knobs

• | Full defrost--Causes the mode motors to direct all air to the windshield and aide window outlets for maximum defrosting.

• | Air intake--Switches between fresh air intake, the default, and recirculating air. Airflow arrows on the display indicate the mode in effect.

• | Full auto switch--Maintains the set temperature automatically. In this mode, the fully automatic temperature control (FATC) system controls the following:

- | The air mix door motor

- | The mode door motor

- | The blower motor speed

- | The inlet air door motor

- | A/C ON/OFF

• | OFF switch--Turns the automatic air conditioning and fan control off.

• | Mode switch--Allows manual selection of the airflow direction.

- | Selection is shown on the function display.

- | Each time the mode switch is pressed, the next function is displayed.

• | A/C switch--Allows manual selection and control of the air conditioning function.

• | Defogger switch--Turns ON the electric defogging heater in the rear window and the outside rearview mirrors, if the vehicle is equipped with heated mirrors.

• | Fan control rotary knob--Allows for manual selection of the fan speed.

### Pressure Transducer

Pressure transducer switching incorporates the functions of the high-pressure and the low-pressure cutout switches along with the fan cycling switch. The pressure transducer is located in the high-side liquid refrigerant line behind the right strut tower, between the right strut tower and the front of dash. The output from this pressure transducer goes to the electronic control module (ECM), which controls the compressor function based on the pressure signal.

### Wide-Open Throttle (WOT) Compressor Cutoff

During full-throttle acceleration, the throttle position (TP) sensor sends a signal to the ECM, which then controls the compressor clutch.

### High RPM Cutoff

As engine RPM approached the maximum limit, the ECM will disengage the compressor clutch until the engine slows the a lower RPM.