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

MODELS 171.4

Fig 1: Battery Charge/Alternator Monitoring Function - Communication Diagram

Courtesy of MERCEDES-BENZ USA

Battery charge/alternator check

The message "BATTERY/ALTERNATOR, LOCATE WORKSHOP" which in the event of a fault is shown in the upper multifunction display (A1p13) has display priority 1.

It appears when the alternator (G2) is not operating correctly. This is the case when "terminal 61 is LOW" and the engine speed is > 200 rpm. There is no message when "terminal 61 is OFF" (engine is off).

Pre-excitation current for the alternator (G2)

The excitation winding is supplied with pre-excitation current via a resistor which is located in the driver-side SAM control unit with fuse and relay module (N10/1). When "terminal 15 is ON " the voltage at terminal 61 is low, as the excitation winding almost short-circuits the voltage downstream of terminal 31. If the alternator voltage rises above the battery voltage when the engine is running, the excitation winding is supplied by the alternator (G2). The voltage at term. 61 increases to the same voltage as the generator voltage.

Networking

The following signals are required by the Controller Area Network bus class B (CAN-B) or Controller Area Network bus class C (CAN-C):

The signal "terminal 61" of the alternator (G2)for alternator check is read in by the driver-side SAM control unit with fuse and relay module (N10/1).
The driver-side SAM control unit with fuse and relay module (N10/1) places the signal "terminal 61 HIGH" on CAN-B when the voltage in terminal 61 is > 9 V.
The driver-side SAM control unit with fuse and relay module (N10/1) places the signal "terminal 61 LOW" on CAN-B when the voltage in terminal 61 is < 4.5 V.
The pulses of the crankshaft position sensor (L5) are read in by the motor electronics control unit (N3/10) and placed in rpm on the CAN C.
The instrument cluster (A1) receives these signals and evaluates them.

Terminal 61 for alternator check

The CAN message "term. 61" can have the status "high" and "low". The status depends on the actual voltage at the input of the driver side SAM control unit with fuse and relay module (N10/1). The status is "HIGH" when the voltage at terminal 61 is > 9 V and is LOW when the voltage is < 4.5 V.

The function of the battery charge/alternator check is in close connection with the functions of the indicator lamp test and engine running detection of terminal 61e.

Instrument cluster (IC), location/task

GF54.30-P-3039SK