Battery charge/alternator monitoring, function - GF54.30-P-3027T

MODEL 211.0/2 as of 1.6.06 except CODE (494) USA version except CODE (498) Japan version

MODEL 211.0/2 as of 1.7.06 with CODE (494) USA version with CODE (498) Japan version

Networking, shown with engine 272

Fig 1: Networking Of Components To Monitor Battery Charge/Alternator

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Battery charge indicator lamp and alternator indicator lamp

In the event of a fault in the power generator the battery symbol and message "Locate workshop" (this message belongs to category 2) or "Stop - battery/alternator" (this message belongs to category 1) are displayed in the multifunction display in the instrument cluster.

The message appears if the alternator is not working correctly (circuit 61), but the engine speed is higher than 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 alternator monitor
Signal "circuit 61 (D+)" from alternator

The alternator indicator lamp "circuit 61" is read in by the driver-side SAM control unit with fuse and relay module. The driver-side SAM control unit with fuse and relay module then places the message "circuit 61 HIGH" (voltage circuit 61 > 9 V) or "circuit 61 LOW" (alternator not working correctly) on the Controller Area Network bus Class B (interior) (CAN B).

Engine speed

The pulses from the crankshaft Hall sensor are read in by the ME-SFI [ME] control unit or by the CDI control unit (N3/9). The respective control unit places the message motor speed (in RPM) on 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 "term. 61" can have the status "high" and "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 greater then 9 V. It is "LOW" when the voltage drops back below 4.5 V.

Excitation current for the alternator

Once circuit 15 is switched on the battery current flows via the alternator preresistance, which is located in the wiring harness, through the excitation winding in the rotor and via the regulator to circuit 31.

The preexcitation is introduced in the process. 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.

Instrument cluster, component description

GF54.30-P-6000TM