Automatic HVAC Description and Operation (LHD)

Automatic HVAC Description and Operation (LHD)

HVAC Unit Construction, Components and Associated Sensors

In-Car Temperature Sensor





The in-car temperature sensor is an NTC thermistor used to monitor the vehicles's interior temperature. Resistance signals are constantly monitored by the OCC module and are used for subsequent control of the OCC system.

It is essential that the venturi and aspirator tube assembly by properly connected to the in-car temperature sensor if the sensor is to provide correct information to the OCC module.

The in-car temperature sensor (1) is located on the left-hand side of the steering column behind the sensor inlet air holes on the instrument cluster trim assembly.

Evaporator Temperature Sensor





The evaporative temperature sensor is an NTC thermistor used to monitor the temperature of the air into the HVAC unit after it has passed through the evaporator core. Resistance values are constantly monitored by the OCC module and are used for subsequent control of the OCC system.

The evaporative temperature sensor (1) is located on evaporator core (2) by a plastic retaining clip (3). The installation point of the sensor to the evaporator is critical for correct OCC system performance.

It is an NTC thermistor used to monitor the ambient (outside) temperature. This sensor is slow reacting due to the dense plastic housing surrounding it. The OCC takes into account road speed before updating the temperature display to avoid false readings in heavy traffic or extended idle conditions.

Resistance signals are sent directly from the ambient temperature sensor to the OCC module for interpretation.