Alternator interface function - GF07.10-P-1009MM
ENGINE 276.9 in MODEL 204
ENGINE 276.9 in MODEL 207, 212 (except 212.095), 218 up to model year 2014
Function requirements for the alternator interface, general points
- Circuit 87M (engine timing ON)
- Engine running
Alternator interface, general points
Using the alternator interface, messages are exchanged via the drivetrain 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. The ME-SFI [ME] control unit reads in the following sensor and signals for this purpose:
- crankshaft Hall sensor (B70), engine speed
- on-board electrical system battery (G1), on-board electrical system voltage via "Circuit 30"
- alternator, status via 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 the engine load, thus also reducing fuel consumption and reduces exhaust gas emissions.
The ME-SFI [ME] control unit controls the following functions:
- switching on of the alternator depending on the on-board electrical system voltage and the demands from the engine.
- regulation of the alternator according to characteristic 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 regulation voltage with a delay in the event of frequent load change at the alternator when idling to stabilize the idling speed.
- protecting the alternator against overheating.
- generating a circuit 61 signal (alternator in operation).
- recognized faults via the chassis CAN (CAN E) to the instrument cluster (A1) for actuation of the respective warning lamp and display messages.
- maintains the regulation voltage at a low value and arranges increased charging of the on-board electrical system battery 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, on-board electrical system battery voltage, time since engine start) and thus detects any alternator faults.
The following faults are identified:
- Line of the alternator interface (drivetrain LIN) has an open circuit or the interface driver in the ME-SFI [ME] control unit is defective (the alternator regulates in this case to 14.3 V)
- electrical and mechanical fault at the alternator:
- control or diodes defective
- stator interruption or short circuit
- excitation interruption
- regulation voltage and charging current not achieved
- regulation voltage too high
- a 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 204 | PE07.10-P-2709-97FAK |
| MODEL 207 | PE07.10-P-2709-97EAH | |
| MODEL 212 | PE07.10-P-2709-97DAI | |
| Model 218 | PE07.10-P-2709-97XAB | |
| Overview of system components for gasoline injection and ignition system with direct injection | ENGINE 276.9 in MODEL 204 ENGINE 276.9 in MODEL 207, 212 (except 212.095), 218 up to model year 2014 | GF07.70-P-9998MM |