Fiat 1996 Brava Service Manual page 216

Engine
Fuel system
Bravo-Brava ^
TD
10.
Preheating control unit
The glow plugs are controlled by the pre­
heating control unit under the direct control
of the electronic control unit.
The unit contains a smart relay which sends
feedback to the electronic control unit in or­
der to inform it of faults in the preheating unit
or short-circuits in the glow plugs.
The figure shows the connectors located on
the base of the preheating control unit and
the pin-outs.
Connections
1. Vehicle earth
2. Not connected
3. Ignition switch (+15)
4. Electronic control unit (pre-postheating
activation)
5. Electronic control unit (fault diagnosis)
8. Battery positive
9. Glow plugs
10. Glow plugs
Air temperature sensor
The intake air temperature sensor is separate
from the air flow meter in this version. It is a
normal Negative Temperature Coefficient
(NTC) sensor: its electric resistance drops as
temperature increases.
Because the control unit input circuit is de­
signed as a voltage divider, this voltage is
distributed between a resistance in the con­
trol unit and the sensor NTC resistance.
The control unit is therefore able to assess
sensor resistance changes through voltage
changes and obtain temperature information.
16
Publication no. 506.670/06