GF54.30-D-3027H Battery Charge/Alternator Monitoring, Function
GF54.30-D-3027H Battery Charge/Alternator Monitoring, Function
Shown with engine 272 and with code (JK3) High-end instrument cluster standard with speedometer in km
A1 Instrument cluster
B70 Crankshaft sensor
G2/7 Alternator
N3/23 ME control unit
N10 SAM control unit
Battery charge/alternator monitor with code (JK3) High-end instrument cluster standard with speedometer in km
If there is a fault in the alternator, the battery symbol and the "Visit workshop" message (category 2 message) appear on the display (A1p1) in the instrument cluster. The messages appear if the alternator is not functioning correctly (Circuit 61) but the engine speed is > 200 rpm. There is no message when the engine is OFF.
Battery charge/alternator monitor except code (JK3) High-end instrument cluster standard with speedometer in km
If there is a fault in the alternator, the alternator warning lamp (A1e7) is actuated in the instrument cluster. The alternator warning lamp is active if the alternator is not functioning correctly (circuit 61) but the engine speed is > 200 rpm.
Networking
The following Controller Area Network (data bus/CAN bus) (CAN) messages are required:
- Circuit 61 (W) alternator check
- The signal "circuit 61 (D+)" from the alternator
The alternator monitor (circuit 61) is read in by the SAM control unit.
The SAM control unit then places the message "circuit 61 HIGH" (voltage on circuit 61 > 9 V) or "circuit 61 LOW" (alternator not functioning correctly) on the Controller Area Network bus class B (interior) (CAN-B).
Determining the engine speed:
- The rotational speed is detected by the crankshaft sensor.
- The signals from the crankshaft sensor are read in by the CDI control unit (N3/20), the CDI control unit (N3/21) or the ME-SFI [ME] control unit (N3/23) and placed on the Controller Area Network bus class C (engine compartment) (CAN-C).
- The instrument cluster receives these signals and processes them.
Alternator check, circuit 61 (D+)
The CAN message "circuit 61" can assume the status "HIGH" or "LOW". The status depends on the actual voltage at the input of the SAM control unit. The status is "HIGH" if the voltage is > 9 V. The status is "LOW" if the voltage drops back to < 4.5 V.
Excitation current for the alternator
When circuit 15 is switched on, the battery current flows via the alternator series resistor, which is located in the wiring harness, through the excitation winding in the rotor and via the governor to circuit 31. This initiates pre-excitation. At low engine speeds self-excitation is nonfunctional, so pre-excitation takes place. If, when the engine is running, the alternator voltage rises above the battery voltage, the excitation winding is supplied by the alternator itself. The voltage at circuit 61 increases to the same voltage as the alternator voltage. If the alternator voltage drops below the battery voltage, this is detected by the SAM control unit and is passed on to the instrument cluster as a CAN message. The instrument cluster then outputs an appropriate warning.
