Functional Description

Functional Description

The electronic control unit automatically operates the system controlling the thermodynamic parameters in order to provide the climatic comfort (temperature and humidity) required by the occupants of the car.

The control unit Q21 is supplied directly at pin 11 by the line of wander fuse Q65; the key-operated supply reaches pin 25 by the line of fuse F17 of G1 (box "A") or fuse F15 (box "C"). Pin 3 and 13 are at earth (G148b).

The outside temperature sensor Q24 is on the right wing mirror: it is an NTC sensor connected to pin 15 of Q21 and connected to the reference earth at pin 12 of Q21.

The antifrost sensor Q26 is inside the duct/distributor unit near the evaporator: it is an NTC sensor connected to pin 18 of Q21 (reference earth at pin 12).

The treated air temperature sensor Q25 is inside the duct/distributor unit upstream of the distribution ports: this is an NTC sensor connected to pin 6 of Q21 (reference earth at pin 12).

The fan control potentiometer Q4 is connected with the corresponding knob: it is supplied by the control unit with 5V (pin 10) and reference earth (pin 12) and returns a signal corresponding to the different positions of the knob (pin 4).

The required temperature control potentiometer Q34 is connected with the corresponding knob: it is supplied by the control unit with 5V (pin 10) and the reference earth (pin 12) and returns a signal corresponding to the position of the knob (pin 5).

The "fast defrosting" switch Q72 is on the distribution knob: this is an N.O. contact which sends a voltage signal (12V) to pin 1 of Q21 and to the compressor switch Q68.

The passenger compartment air temperature sensor Q33 is on the dashboard, on the right of the steering wheel. This is an NTC sensor connected to pin 14 of Q21.

The sensor is "ventilated", i.e. it contains a small fan that is always supplied (line of F17 box G1 "A" - or F15 for box G1 "C" - and earth G148b and earth G148b) so that the temperature reading remains unaffected by the air stagnating inside the dashboard.

The mixing control actuator Q30 is driven by the control unit of pin 22 and 23. A motor supplied at 12V controls the rotary movement of a draw pin which acts directly on the mixing port. A potentiometer detects the position and acts as "feedback" to the control unit (pin 17).

The recirculation control actuator Q27 is a motor supplied at 12V by pin 26 and 27 of Q21 which turns the outside air inlet port in the two directions to the end of its stroke, without intermediate positions.

The fan Q1 that sends outside or recirculation air to the duct-distributor is supplied at 12V by the special line of fuse F13 of G1 and it is controlled at different speeds continuously by an electronic regulator Q31 near to it.

At the input, the electronic regulator Q31 receives a control signal from the control unit - pin 20 and 21 - and converts it into an earth signal of variable power continuously so as to operate the fan accordingly.

Switches Q68 enable engagement of the compressor and recirculation connecting to pin 25 and 7 of Q21; inside the set of switches the leds are lit when the sidelights are on, and also the whole control panel, through lights F8 and the line of connector D of G1.

Lastly the diagnosis connector T10, near the control unit; connects to pin 8 and 9 of Q21.