Control System Inputs

HVAC Module 

The HVAC module:

• is located in the instrument panel.
• has a vacuum fluorescent display for displaying set temperature, ambient temperature, function and DTCs.
• utilizes an on-board diagnostic (OBD) feature to supply the technician with DTCs. These DTCs help direct the technician to the inoperative component.

Rear Audio/Climate Control Module 

The rear audio/climate control module is equipped on limousine (long wheelbase) vehicles. The rear audio/climate control module converts an input from the rear audio/climate control switch, then signals the audio control module (ACM) via the audio corporate protocol (ACP) bus. The ACM then signals the HVAC module over the J1850 communications network (standard corporate protocol [SCP] bus).

Steering Wheel Audio/Climate Control Switch 

The steering wheel audio/climate control switch, located on the right side of the steering wheel, allows the driver to adjust the passenger compartment temperature setting. For removal and installation of the steering wheel audio/climate control switch, refer to INFORMATION & ENTERTAINMENT SYSTEMS article.

Ambient Air Temperature Sensor 

The A/C ambient air temperature sensor:

• is located in front of the A/C condenser core near the center of the vehicle.
• contains a thermistor which measures the temperature of outside air as a resistance and sends that reading to the HVAC module.

In-Vehicle Temperature Sensor 

The in-vehicle temperature sensor operates in the following manner:

• A thermistor in the in-vehicle temperature sensor measures air temperature inside the passenger compartment.
• An automatic temperature control sensor hose and elbow is connected between the A/C evaporator housing and the in-vehicle temperature sensor.
• The automatic temperature control sensor hose and elbow takes air from the A/C evaporator housing air stream to create a suction in the in-vehicle temperature sensor.
• The suction draws in-vehicle air into the in-vehicle temperature sensor and across the thermistor.

Solar Amplifier (Sunload Sensor) 

The solar amplifier supplies information to the HVAC module indicating sunload. For information on the location and service of the solar amplifier, refer to EXTERIOR LIGHTING article.