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

Engine 178.9 In Model 190 

Function requirements for the alternator interface, general points 

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

The " Engine running" function requirements include all function sequences of the fuel low pressure and fuel high-pressure circuit, as described in the "Fuel supply" function.

Alternator interface, general points 

With the alternator interface, messages (for example the "Dynamo-Field-Monitor-Signal") are exchanged via the drive LIN (LIN C1) between the alternator (G2) and the ME-SFI [ME] control unit (N3/10) and the control response of the alternator is controlled.

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 dynamo field monitor signal.

The maximum data transmission rate between the ME-SFI [ME] control unit and the LIN control for the alternator is 19.2 kbit/s. The LIN control has no direct outputs. The ME-SFI [ME] control unit reads in the following signals:

• Crankshaft Hall sensor (B70), engine RPM
• Battery (G1), on-board electrical system voltage over "circuit 30"
• Alternator, status via the drive LIN

Function sequence for alternator interface 

The ME-SFI [ME] control unit regulates the control response of the alternator, for example in order to reduce the charging voltage when idling if the on-board electrical system battery is sufficiently charged.

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

The ME-SFI [ME] control unit controls the following functions:

• Switching on of the alternator depending on the condition of the on-board electrical system and the requirements from the engine
• Regulation of the alternator according to the characteristics maps stored in the ME-SFI [ME] control unit; the charging voltage is prescribed by the ME-SFI [ME] control unit for this
• Delayed adaptation of the charging voltage in the event of frequent load changes at the alternator when in idle (to stabilize the idling speed).
• Protecting the alternator against overheating.
• Generation of a "circuit 61 signal" (alternator in operation).
• Sending detected faults via the drive train CAN (CAN C1), powertrain control unit (N127), chassis CAN 1 (CAN E1) to the electronic ignition lock control unit (N93/9) and user interface CAN (CAN HMI) to the instrument cluster (A1) for actuation of the corresponding warning lamps and display messages.
• Keep the charging voltage at a low level and charge the battery more strongly in the deceleration phases (fuel saving)

The alternator performs continuous self-diagnosis and transmits the results when requested to the ME-SFI [ME] control unit. This compares the results with other signals (for example, engine RPM, on-board electrical system voltage, time since engine start) and thus detects any alternator faults.

The following faults are identified:

• Line for the alternator interface (drive train LIN) has an open circuit or the interface driver in the ME-SFI [ME] control unit is defective (the alternator regulates in this case at 14.3 V).
• 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

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

Using information received by the ME-SFI [ME] control unit over the alternator interface, the "circuit 61 signal" is simulated in the ME-SFI [ME] control unit and issued over the CAN network (e.g. for the IC).

	Electrical function schematic for alternator interface		PE07.10-P-2709-97HBA
	Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-P-9998MNB