GF07.10-P-1009OGG Alternator Interface Function

GF07.10-P-1009OGG Alternator Interface Function
- refinement package
- as of model year 2009


Function requirements for the alternator interface, general points
^ Circuit. 87 ON (engine control ON)
^ Engine running

Alternator interface, general points
Using the alternator interface, messages are exchanged over the drive LIN (LIN C1) between the alternator (G2) and the CDI control unit (N3/9), in order to regulate the alternator control response. For this purpose, the CDI control unit reads in the following sensor and signal:
- Crankshaft Hall sensor (B70), engine speed
- Battery voltage (G1) through "tml. 30"

Alternator interface function sequence
The CDI control unit regulates the alternator control response, for example in order to reduce the regulation voltage (charging voltage) when the battery is sufficiently charged. This reduces engine load thus lowering the fuel consumption and improving the exhaust gas emissions.

The CDI control unit actuates the following functions:
- Switching on the alternator after engine start.
- Regulation of the alternator according to performance maps stored in the CDI control unit. To do this, the control voltage is preset by the CDI control unit.
- Adapting the control voltage with a delay in the event of frequent load changes at the alternator to stabilize the idling speed.
- Protecting the alternator against overheating.
- Generating of a "circuit 61 signal" (alternator in function).
- Reporting detected faults to the instrument cluster (A1) for actuation of the respective warning lamps and display messages.

The alternator constantly performs a self-diagnosis and sends the results when requested to the CDI control unit. This compares the results with other signals (for example, engine rpm, battery voltage, time since engine start) and thus detects any alternator faults.

The following faults are identified:
- Short circuit or open circuit on the "circuit 61" output of the CDI control unit.
- Open circuit on alternator interface line (drive LIN) or interface driver fault in the CDI control unit. For this type of fault, a regulation voltage of 13.45 up to 14.15 V is given.
- Electrical and mechanical faults at alternator:
- controller or diodes defective
- stator interruption or short circuit
- excitation circuit open
- regulation voltage and charging current not reached
- regulation voltage too high
- cracked or loose poly-V belt

Diagnosis
In order to check the regulation voltage, the battery must be placed under load using a battery tester since the regulation voltage can be reduced significantly when the battery is fully charged and under no load.

"Circuit 61 signal"
For alternators with an alternator interface, line "circuit 61" is not needed. Using information received by the CDI control unit over the alternator interface, the "circuit 61 signal" is simulated in the CDI control unit and sent through an output stage connected to ground (e.g. for the instrument cluster).