Fiat 1998 Marea Service Manual page 285

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MANAGEMENT OF THE CLIMATE CONTROL SYSTEM
The Hitachi engine management control unit is functionally connected to the climate control system in as
far as:
1. it receives the request to switch on the compressor via pin 9/B and operates the interventions (addi-
tional air);
2. it gives the go ahead to switch on the compressor via pin 10/B when the strategy conditions are veri-
fied;
3. it receives information concerning the state of the three stage pressure switch from pin 27/B and oper-
ates the interventions (radiator fan operation).
As far as point 1 is concerned, if the engine is idling, the control unit increases the air flow rate passing
from the idle actuator in advance of the compressor being switched on and, conversely, it returns the ac-
tuator to its normal position after the compressor is switched off.
As far, on the other hand, as point 2 is concerned, the control unit automatically switches off the com-
pressor:
- for 6 sees (timed disengagement):
- in butterfly opening conditions above 70°,
- during vehicle take-off;
- as long as the critical conditions persist:
- at engine coolant temperatures above 114°C,
- at engine speeds below 750 rpm.
1. Compressor
2. Compressor relay feed
3. Fuse box
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4. Battery
5. Climate control unit
6. Three stage pressure switch
Engine
Fuel system
10.
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