Automatic Climate Control

The driver sets a target temperature instead of a heater position, and the system works out how to reach and hold it. It uses sensors for cabin temperature, outside temperature, sunlight and sometimes humidity and air quality. Dual-zone or multi-zone systems allow different temperatures for driver, passenger and rear seats.

A control unit compares the measured temperatures with the target and controls the blend doors, blower speed and air-conditioning compressor.

If the system blows hot or cold unexpectedly, a faulty sensor, actuator or low refrigerant charge are common causes. Many systems store fault codes that can be read with a scan tool, and some have a built-in self-test started from the control panel.