GF54.30-P-3027TX Battery Charge/Alternator Monitoring, Function

GF54.30-P-3027TX Battery Charge/alternator Monitoring, Function

Component Identification:

Battery charge/alternator check
In the event of a fault in the alternator, the instrument cluster in the multifunction display shows the battery symbol and the message "Visit Workshop" (Category 2 message) or "Battery/ Alternator - Stop." (Category 1 message). 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.

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 check "circuit 61" is actuated by the driver-side SAM control unit with fuse and relay module. This control unit then passes the message "Circuit 61 HIGH" (voltage at circuit 61 > 9 V) or "Circuit 61 LOW" (alternator not functioning correctly) to the class B (interior) Controller Area Network bus (CAN-B).

Engine speed
The pulses from the crankshaft position sensor or the crankshaft Hall sensor are registered by the ME-SFI [ME] control unit or CDI control unit. The respective control unit relays the engine speed message (in rpm) to the Controller Area Network bus class C (engine compartment) (CAN-C). The instrument cluster receives these messages and evaluates them.

Alternator check, circuit 61 (D+)
The CAN message "circuit 61" can assume the status "HIGH" or "LOW". The respective status depends on the actual voltage at the input of the driver-side SAM control unit with fuse and relay module. 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 tml. 61 increases to the same voltage as the alternator voltage. If the alternator voltage drops below the battery voltage, this is detected by the driver-side SAM control unit with fuse and relay module and relayed as a CAN message to the instrument cluster, which outputs an appropriate message via the multifunction display.