Fiat 1996 Brava Service Manual page 403

Engine
Fuel system
Bravo-Brava ^
TD100
10.
Pre-heating control unit
The operation of the heater plugs takes place
via the pre-heating control unit, under the di­
rect control of the electronic control unit.
There is an "intelligent" relay inside which
sends a return response (feed-back) to the
injection control unit which is informed in
this way of any failures of the pre-heating
control unit or short circuit to earth of the
heater plugs.
The diagram shows the connectors on the
pre-heating control unit base and the rele­
vant pin-out.
Connections
1. Vehicle earth
2. Not connected
3. Ignition switch (+15)
4. Electronic control unit (pre-post heating
activation)
5. Electronic control unit (fault diagnosis)
8. Battery positive
9. Heater pJugs
10. Heater plugs
Air temperature sensor
The intake air temperature sensor is, on this
version, separate from the air flow meter: it
comprises a standard NTC (Negative Tem­
perature Coefficient) where the electrical re­
sistance decreases as the temperature in­
creases.
Since the control unit intake circuit is de­
signed as a voltage divider, this voltage is di­
vided between a resistance in the control unit
and the sensor NTC resistance.
As a result the control unit is capable of eval­
uating the variations in the sensor resistance
through the changes in voltage and thereby
obtain information concerning the tempera­
ture.
24
IX-96 - Update
Print no. 506.670/08