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

ENGINE 281.910 in MODEL 453.0/3/4 

Function requirements for the alternator interface, general points 

• Circuit 87 (Engine management ON)
• Engine runs

Alternator interface, general points 

Messages are exchanged between the driver-side SAM control unit (N1011) and the alternator (G2) via the drive LIN (LIN C1) and communicates via the interior CAN (CAN B) with the ME-SFI [ME] control unit (N3/10) and therefore controls the control response of the alternator. To do this there is delayed adaptation of the charging voltage for a larger change in load of the alternator. The current operating rate of the alternator is transmitted by the driver-side SAM control unit to the ME-SFI [ME] control unit. The ME-SFI [ME] control unit reads in the following signals:

• Crankshaft position sensor (L5), engine speed
• On-board electrical system battery (G1), on-board electrical system voltage over "circuit 30"
• Alternator, status via driver-side SAM control unit and interior CAN

Function sequence for alternator interface 

The control response of the alternator is communicated between the ME-SFI [ME] control unit and the driver-side SAM control unit.

the ME-SFI [ME] control unit and the driver-side SAM control unit control the following functions:

• Adapting the charging voltage with a delay in the event of frequent load changes at the alternator in idle to stabilize the idling speed.
• Protecting the alternator against overheating.
• Recognized errors via the interior CAN to the IC control unit (IC) (A1), for actuation of the respective indicator lamps and display messages.
• The ME-SFI [ME] control unit calculates the specified value of the charging voltage for optimal running of the alternator.
• The driver-side SAM control unit transmits the charge level of the on-board electrical system battery and the output of the switched on electrical consumer to the ME-SFI [ME] control unit.

  Idle regulation 

• If the charge level of the on-board electrical system battery is high, (about 100%) the ME-SFI [ME] control unit does not increase the idle speed.
• If the charge level of the on-board electrical system battery is at a low level, the on-board electrical system battery is charged by an increased idle speed control. Adaptation takes place by means of idle speed control.

  Regulation under engine load 

• If the charge level of the on-board electrical system battery is at a high level then the on-board electrical system battery is permanently under no load.
• If the charge level of the on-board electrical system battery is at a center level, the driver-side SAM control unit requests loading of the on-board electrical system battery.
• If the charge level of the on-board electrical system battery is at a low level, the alternator is actuated by the driver-side SAM control unit.

Regulation reduces the engine loading, whereby less fuel is consumed and the exhaust emissions are reduced.

The alternator performs continuous self-diagnosis and sends the results via the drive LIN, driver-side SAM control unit and interior CAN to the ME-SFI [ME] 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:

• Open circuit line for the bit synchronous drive-LIN interface or defect in interface driver of the driver-side SAM control unit
• Electrical and mechanical fault at the alternator:
  • Control or diodes defective
  • Stator interruption or short circuit
  • Excitation interruption
  • The charging voltage and charging current are not reached
  • Charging voltage too high
  • A cracked or loose poly-V belt

Diagnosis

A battery tester must be used to place a load on the on-board electrical system battery in order to check the charging voltage, since the charging voltage can be significantly reduced when the on-board electrical system battery is fully charged and under no load.

	Electrical function schematic for alternator interface		PE07.10-P-2709-97BBA
	Overview of system components motor electronics (ME-SFI) fuel injection and ignition system		GF07.61-P-9997KJ