Alternator Interface Function - GF07.10-P-1009OLG

ENGINE 651.9 in MODEL 166 up to model year 2016 

Function requirements for the alternator interface, general points 

• Circuit 87M (engine management ON)
• Engine runs

Alternator interface, general points 

Using the alternator interface, messages are exchanged over the drive train LIN (LIN C1) between the alternator (G2) and the CDI control unit (N3/9) and the control response of the alternator is controlled. To do this the CDI control unit reads in the following sensor and signals:

• Crankshaft Hall sensor (B70), engine rpm
• On-board electrical system battery voltage (G1) over "circuit 30"
• Alternator, status

Function sequence for alternator interface 

The CDI control unit regulates the alternator control response, for example in order to reduce the charging voltage when the on-board electrical system battery is sufficiently charged.

This reduces the engine load, thus also reducing fuel consumption and improving exhaust emissions.

The CDI control unit controls the following functions:

• Switching on of the alternator dependent on the condition of the on-board electrical system and on the requirements from the engine.
• Regulation of the alternator based on characteristics maps stored in the CDI control unit. To do this, the charging voltage is prescribed by the CDI control unit.
• Protecting the alternator against overheating.
• Adapting the charging voltage with a delay in the event of frequent load changes at the alternator in idle to stabilize the idling speed.
• Report recognized faults to the instrument cluster (A1) for actuation of the corresponding warning lamps and display messages via chassis CAN 1 (CAN E1), electronic ignition lock control unit (N73) and chassis CAN 2 (CAN 2).
• Keeping on-board electrical system voltage at a low value and charging the on-board electrical system battery more strongly in the deceleration phases (fuel saving).
• Generation of a "circuit 61 signal" (alternator in operation).

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

The following faults are identified:

• Line (drivetrain LINE) for the alternator interface has an open circuit or the interface driver in the CDI control unit is defective (the alternator regulates in this case at 14.3 V).
• Electrical fault at alternator

• Possible causes: alternator regulator or diodes defective, stator defective or excitation circuit open
• Possible consequences: charging voltage or charging current not adequate or too high

• Mechanical fault on the alternator

• Possible causes: a cracked or loose poly-V belt
• Possible consequences: no or poor charging of the battery, no or poor on-board electrical system supply

Diagnosis

To check the charging voltage, the on-board electrical system battery must be loaded with a battery tester since the charging voltage can be significantly reduced when the on-board electrical system battery is fully charged and under no load.

Circuit 61 signal

For alternators with an alternator interface the "circuit 61" line 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 issued over the CAN network (e.g. for the IC).

	Electrical function schematic for alternator interface		PE07.10-P-2709-97NAA
	Overview of system components for common rail diesel injection (CDI)		GF07.16-P-9997OLG