ME-SFI alternator interface function - GF07.61-P-3003MAS

ENGINES 156.984 in MODEL 216.377, 221.077 /177 as of Model Year 09 /AEJ 08 

Function requirements for the alternator interface, general points 

• Circuit 87M ON (engine control ON)
• Engine running

Alternator interface, general points 

Through the alternator interface, messages are exchanged over the drive LIN (LIN C1) between the alternator (G2) and the ME-SFI control unit (N3/10), in order to regulate the alternator control response. For this purpose, the ME-SFI control unit reads the following sensor and signal:

• Crankshaft Hall sensor (B70), motor speed
• On-board electrical system battery voltage (G1) through "circuit 30"

Alternator interface function sequence 

The ME-SFI 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 the exhaust gas emissions.

The ME-SFI control unit controls the following functions:

• Switching on the alternator after engine start.
• Regulation of the alternator according to performance maps stored in the ME-SFI [ME] control unit. To do this, the control voltage is preset by the ME-SFI [ME] 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 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 self-diagnosis and sends the results when requested 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:

• Short circuit or discontinuity at output "terminal 61" from ME-SFI [ME] control unit.
• Open circuit on alternator interface line (drive LIN) or interface driver fault in the ME-SFI 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
• exciter interruption
• regulation voltage and charging current not reached
• regulation voltage too high
• cracked or loose poly-V belt

Diagnosis

To check the regulation voltage, the on-board electrical system battery must be loaded with a battery tester, as the regulation voltage can be significantly reduced when the on-board electrical system battery is under full or no load.

"Terminal 61 signal"

For alternators with an alternator interface, line "terminal 61" is not needed. From information which the ME-SFI [ME] control unit receives via the alternator interface, the "terminal 61 signal" is simulated in the ME-SFI [ME] control unit and is emitted via an output stage switching to ground (e.g. for the instrument cluster).

	Electrical function schematic, alternator interface ME	Model 216	PE07.61-P-2755-97CAC
		Model 221	PE07.61-P-2755-97SAC
	ME-SFI [ME] control unit, component description	N3/10	GF07.61-P-6000MAS