Functional Description

Functional Description

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

This fan is always supplied by battery voltage through the line protected by the specific wander fuse G254, to be found next to the branch terminal box: it is therefore operated by an earth signal: this signal arrives directly (2nd speed) or through the additional resistance O22 (1st speed), fitted with a thermal safety contact.

The delaying device Q42, together with relay I99b - present only up to chassis no..... - , controls the gradual engagement of the fan P2, operating according to the following logic:

The voltage leading - up to chassis no..... - from the compressor disengagement control unit Q67 (12V with compressor engaged) and - from chassis no..... - directly from the ignition switch - supplies the coil and the electronic devices of the delaying device Q42 -pin 85 and relay I99b - where fitted - ; the coil of Q42 is energised by an earth signal -pin P- which leads from the trinary pressure switch Q20: this causes the immediate sending of a signal - pin 30- to energise relay

I99a or I99b, which sends the earth signal for the fan P2 through the additional resistance O22: 1st speed.

After appr. 8-12 seconds, if the signal leading from the trinary persists, the delaying device operates the second speed with an earth signal from pin 86, which energises relay I100 that sends the earth signal directly to the fan P2: 2nd speed.

When the pressure switch signal ceases, the fan is immediately disengaged.

The fan is operated at the two different speeds also by the two- level thermal contact L33 which controls the temperature of the coolant in the engine radiator: when a first level is reached, relay I99a is energised, located in the fuxebx G1, which sends the earth signal to the fan P2 through resistance O22: 1st speed.

If the second temperature level is reached, relay I100 is energised, located on the fan duct, which sends the earth signal directly to the fan P2: 2nd speed.

The delaying device Q42 and relay I99b are located - up to chassis no..... - in the set of relays and fuses Q41.