ME-SFI alternator interface function - GF07.61-P-3003MOS
ENGINES 275.953 in MODEL 216.376, 221.176 as of model year 2009 /YoM 08
ENGINES 275.982 in MODEL 216.379, 221.179 as of model year 2009 / YoM 08
Function requirements for alternator interface, general points
- Circuit 87M (engine timing unit ON)
- Engine running
Alternator interface, general points
Messages (e.g. the dynamo field monitor signal) are exchanged via the drivetrain LIN (LIN C1) using the alternator interface between the alternator (G2) and the ME-SFI [ME] control unit (N3/10) are exchanged and the control response of the alternator controlled. This includes delayed adaptation of the regulation voltage for a large change in load on the alternator. The current operating rate of the alternator is determined using 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 is not fitted with any direct outputs. The ME-SFI [ME] control unit reads in the following sensor and signals:
- Crankshaft position sensor (L5), engine speed
- On-board electrical system battery voltage (G1) over "circuit 30"
- Alternator, status via the drivetrain LIN
Function sequence for alternator interface
The ME-SFI [ME] 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 engine load, thus also reducing fuel consumption and improving exhaust gas emissions.
The ME-SFI [ME] control unit controls the following functions:
- Switching on of the ALT dependent on the condition of the onboard electrical system and the requirements from the engine.
- 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.
- Generation of a "circuit 61 signal" (alternator in operation).
- Sending of a recognized fault via the chassis CAN (CAN E) and the backbone CAN (CAN F) to the IC (A1) to actuate the respective warning lamps and message displays.
- Keeps regulation voltage at a low value and charges the onboard electrical system battery more strongly in the deceleration phases (fuel saving)
The alternator performs continuous 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, vehicle electrical system battery voltage, time since engine start) and thus detects any alternator faults.
The following faults are identified:
- Line for the alternator interface (drivetrain LIN) has an open circuit or the interface driver in the ME-SFI [ME] control unit is defective (the ALT regulates in this case at 14.3 V).
- 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
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 | Model 216 | PE07.61-P-2755-97CAA | |
| Model 221 | PE07.61-P-2755-97SAA | ||
| Component description for ME-SFI [ME] control unit | N3/10 | GF07.61-P-6000MOS |