Functional Description

Functional Description

The fan P2 provides the necessary ventilation for cooling the engine radiator and air conditioning system condenser.

This fan is always supplied by battery voltage through the line protected by the specific wander fuse G254, located in the branch terminal strip: it is operated by an earth signal: this signal arrives directly (2nd speed) or via the additional resistance O22 (1st speed).

The M2.10.4 injection - ignition control unit controls the fan for cooling the engine coolant fluid and the conditioning system coolant fluid.

This has made it possible to eliminate the thermal contact usually to be found on the radiator. the two fan speeds are operated depending on the engine temperature, detected by the control unit through the special sensor: a “low” (earth) signal leaves pin 26 which controls the 1st speed relay I99, and a “low”

(earth) signal leaves pin 25 which controls the second speed relay I100.

The pressure switch Q20 also sends special signals to the control unit for engaging the fans if the pressure of the coolant fluid in the circuit exceeds certain ratings:

• over 15 bar appr. the signal is sent to pin 44 for engaging 1st speed;
• over 20 bar appr. to pin 43 for the 2nd speed.

The “key-operated” voltage (line of relay I35 protected by fuse F4 of G1 for box “A” or fuse F17 for “B” or fuse F14 for “C”) supplies the coil of relays I99 and I100; which are operated by the above-mentioned earth signals.