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

GF54.30-P-3027SK Battery Charge/alternator Monitoring, Function
- up to model year 08

Component Identification:

Battery charge/alternator check
The message "BATTERY/ALTERNATOR, SERVICE REQUIRED", shown in the upper multifunction display (A1p13) has display priority 1.
It appears when the alternator (G2) is not functioning correctly. This is the case when "circuit 61 is LOW" and the engine speed is > 200 rpm. A message does not appear when "circuit 61 is OFF" (engine is off).

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 "circuit 15 ON", the voltage at circuit 61 is low since the excitation winding almost short circuits the voltage to circuit 31. If, when the engine is running, the alternator voltage rises above the battery voltage, the excitation winding is supplied with current by the alternator (G2). The voltage at circuit 61 increases to the same voltage as the alternator 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 "circuit 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 "Circuit 61 HIGH" on the CAN-B if the circuit 61 voltage is > 9 V.
^ The driver-side SAM control unit with fuse and relay module (N10/1) places the signal "Circuit 61 LOW" on the CAN-B if the circuit 61 voltage is < 4.5 V.
^ The pulses of the crankshaft position sensor (L5) are read by the ME-SFI [ME] control unit (N3/10) and placed on the CAN-C as a per minute value.
^ The instrument cluster (A1) receives these signals and evaluates them.

Circuit 61 for alternator check
The CAN message "circuit 61" can assume the states "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 state becomes "HIGH" if the voltage at circuit 61 exceeds 9 V, and "LOW" if the voltage drops below 4.5 V.

The "battery charge and alternator monitoring" function is closely related to the "indicator lamp check" and "engine operation detection" functions (circuit 61e).