Evaporator temperature sensor

When button is pressed to activate the air conditioner, ECU is supplied with a positive voltage of 12 V at terminal (1) (with contacts 1 and 3 of the three stage pressure switch closed).

Under these conditions, the ECU sends a positive signal to terminal (15) of the fuel injection control unit (1), which activates relay (by means of a negative signal) in order to engage electromagnetic coupling of compressor after a delay of a some microseconds used to compensate for engine idle speed. If evaporator temperature reaches levels of less than 3 °C, the ECU eliminates the positive signal to injection control unit (1) and consequently de-activates the compressor pulley electromagnetic coupling (anti-frost function).

The electromagnetic coupling is also de-activated by the injection ECU (1) in the case of full acceleration and when engine temperature reaches a pre-established threshold, to prevent overheating.

Evaporator temperature sensor

The temperature sensor is an NTC resistor and positioned close to the evaporator outlet pipe. It is not accessible from the outside.

In the case of service operations that involve evaporator removal/refitting, it is important NOT TO MOVE THE SENSOR FROM ITS ORIGINAL POSITION, because the different temperature levels read by a differently positioned sensor could lead to incorrect compressor output control.

Sensor reference values are: