Description of operation

Description of operation

Following the electrical diagram there is a description of operation that analytically describes the diagram, following the "flow" of the signals from the power supply to the earth, explaining the electric logic and the flow of the connections between the different components.

here the components have the same alphanumeric code as indicated on the diagrams (and the relevant key)

Components

In a table, the list of the components involved in the operation and the overview concerning that component, to be able to follow more easily the path to other sections ("Repair procedures", "Description and operation", "Tests").

FUNCTIONAL DESCRIPTION

Circuit control ECU M70 (connector B, pin 5) is powered by an ignition switch (see pK7A), protected by individually fitted fuse B18; the same line powers the other circuits in the system. The ECU (connector B, pin 10) is powered directly from the battery (B8 main fuses J9T1) via junction unit B1 fuse T30. Push-button light operating (when the indicator lights are on) reaches connector B, pin 2 via a stalk switch N9 protected by fuse B11. M70 (connector A, pin 14 is earthed. M70 (connector B, pin 7, receives the tachometer signal from E49. Connector A, pin 1, receives the external temperature measurement from B19.

The internal temperature sensor is located in selector right air-vent P81. The sensor is powered (5 V) by M70 (connector A, pin 14), and sends a signal to connector A, pin 13.

Sensors K87 (lower conditioned air), K88 (upper conditioned air) and K89 (passenger compartment air) are connected to ECU M70 and powered (5 V) by pin 13. They send signals to M70 (connector A, pins 11, 10, and 9 respectively).

Sensor K88 is fitted with an ignition switch powered motor which ensures temperature readings are not affected by stagnant (i.e. warm) air inside the cabin.

only for 5LZ22

Frost sensor: K85 is powered (5 V) by M70 (connector A, pin 13) and sends a signal to connector A, pin 5, which disconnects the condenser if evaporator temperature are too low.

The air conditioning system is equipped with two actuators for air re-circulation (N82, or standing N81) and air distribution (N90).

Air re-circulation actuator N82 is controlled by M70 (connector B, pin 1) and sends a current feedback signal to M70 (connector A, pin 3).

Air blending actuator N90 is controlled by M70 (connector B, pin 8). Temperature control function is powered by connector A, pin 2; it sends a feedback signal to connector B, pin 12.

Air distribution actuator N90 is controlled by M70 (connector B, pin 10). Its position/position control function is powered by connector A, pin 2; it sends a feedback signal to connector B, pin 9.

Electronic regulator M72 operates the fan at several speeds. It receives a control signal from the ECU (connector B, pin 3) which is transformed into a variable voltage signal which controls the fan. Voltage is stabilised, i.e. is independent from battery voltage variations. The regulator is powered by an ignition switched line (pNT4a) and protected by fuse B10; it is earthed and sends a temperature control signal back to M70 (connector A, pin 4).

Fan N98 is powered directly from the battery via B8 main fuse A/C. It is operated at several speeds according to the voltage signal from electronic regulator M72. ECU M70 is equipped with a self-test system which can be accessed via connector F1/V. Signals are sent to connector B, pins 8, via a specific diagnostic line. Headlight window LED and "hard demisting" controls are kept integrated within ECU M40 (from connector B, pin 1, and connector A, pins 6 and 8, respectively important reminder: the climate control will only trigger the push-button wind LED but has no effect on rear window heating logic (see E6320 - REAR WINDOW AND KYTEISCHIR DRIVING MIRROR (INSTRUCTIONS)).

Connector A, pin 7, starts the compressor (see E6021 - COMPRESSOR).