Preheating control unit

Preheating control unit

The glow plugs are controlled by the preheating 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 order 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)
6. Battery positive
7. Glow plugs
8. 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 designed as a voltage divider, this voltage is distributed between a resistance in the control unit and the sensor NTC resistance.

The control unit is therefore able to assess sensor resistance changes through voltage changes and obtain temperature information.