Alternator interface function - GF07.10-P-1009OG

ENGINES 642.8 in MODEL 204.0/2/9, 207.3/4, 212.0/2, 218 

Function requirements for the alternator interface, general points 

• Circuit 87M 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
• On-board electrical system battery voltage (G1) over "circuit 30"

Function sequence for alternator interface 

The CDI control unit controls the alternator control response, for example, in order to reduce the regulation voltage (charging voltage) when the engine is at idle and the on-board electrical system battery is sufficiently charged This reduces the engine load, thus also reducing fuel consumption and improving exhaust gas emissions.

The CDI control unit actuates the following functions:

• Switching on the alternator after engine start.
• Regulation of the alternator based on characteristic maps stored in the CDI control unit. To do this, the control voltage is preset by the CDI control unit.
• Protecting the alternator against overheating.
• Adapting the control voltage with a delay in the event of frequent load changes at the alternator to stabilize the idling speed.
• Generation of a "circuit 61 signal" (alternator in operation).
• Sending of recognized faults to the instrument cluster (A1) via the chassis CAN (CAN E) to actuate 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. The control unit compares the results with other signals (for example, engine RPM, vehicle electrical system battery voltage, time since engine start) and thus detects any alternator faults.

The following faults are identified:

• Short circuit or open circuit on output "circuit 61" of the CDI control unit
• Open circuit on alternator interface line (drive LIN) or interface driver fault in the CDI control unit. (For this fault, a regulation voltage of 13.45 to 14.15 V is specified.)
• 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

To check the regulation voltage, a battery tester must be used to place a load on the on-board electrical system battery, as the regulation 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 the information received by the CDI control unit through 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).

	Electrical function schematic for alternator interface	Model 204	PE07.10-P-2709-97FAH
		Model 207	PE07.10-P-2709-97EAF
		Model 212	PE07.10-P-2709-97DAF
		Model 218	PE07.10-P-2709-97XAA
	Overview of system components for common rail diesel injection (CDI)		GF07.16-P-9997OG