Alternator interface function - GF07.10-P-1009OM
ENGINE 651.9 in MODEL 204
ENGINE 651.9 in MODEL 207, 212 (except 212.098/298) up to model year 2014
ENGINE 651.9 in MODEL 218 up to model year 2014
Function requirements for the alternator interface, general points
- Circuit 87M ON (engine timing ON)
- Engine running
Alternator interface, general points
Using the alternator interface, messages are exchanged via the drive LIN (LIN C1) between the alternator (G2) and the CDI control unit (N3/9) and the control response of the alternator is controlled. For this purpose, the CDI control unit reads in the following sensor and signal:
- Crankshaft position sensor (L5) (except code (B03) ECO start/stop function), engine RPM
- Crankshaft Hall sensor (B70) (with code (B03) ECO start/stop function), engine speed
- On-board electrical system battery voltage (G1) via "circuit 30"
Function sequence for alternator interface
The CDI 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.
Reducing the engine loading in this manner decreases the fuel consumption and reduces exhaust emissions.
The CDI control unit controls the following functions:
- Switching on the alternator after engine start.
- Adapting the regulation voltage with a delay to stabilize the idle speed in the event of frequent load changes at the alternator in idle.
- 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.
The alternator constantly performs a self-diagnosis and sends the results when requested to the CDI 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 open circuit at output "circuit 61" of the CDI control unit.
- Line of the alternator interface (drivetrain LIN) has an open circuit or the interface driver in the CDI control unit is defective. (For this fault, a regulation voltage of 13.45 to 14.15 V is specified.)
- 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
For alternators with an alternator interface the "circuit 61" line is not needed. Using the information received by the CDI control unit through the alternator interface, the "circuit 61 signal" is simulated in the CDI control unit and sent through an output stage connected to ground (e.g. for the instrument cluster).
| Electrical function schematic for alternator interface | MODEL 204 | PE07.10-P-2709-97FAE | |
| Electrical function schematic for alternator interface | MODEL 207 | PE07.10-P-2709-97EAE | |
| Electrical function schematic for alternator interface | MODEL 212 | PE07.10-P-2709-97DAE | |
| Electrical function schematic for alternator interface | MODEL 218 | PE07.10-P-2709-97XAD | |
| Overview of system components for common rail diesel injection (CDI) | GF07.16-P-9997OM |