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

MODEL 164

Networking

Fig 1: Battery Charge/Alternator Monitoring Function Diagram

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Battery charge/alternator check

In the event of an alternator fault the battery symbol and the message "Locate workshop" (this message belongs to category 2) or "Battery/alternator-stop!" is displayed in the multifunction display in the instrument cluster.

This message belongs to Category 1.

It appears when the alternator is not operating correctly (circuit 61), but the engine speed is higher than 200 rpm.

There is no message when the engine is OFF.

Networking

The following CAN messages are required:

"Circuit 61" alternator check
"Terminal 61 (= D +)" from alternator.

The alternator check "circuit 61" is read in by the front SAM control unit.

The front SAM control unit then places the message "terminal 61 HIGH" (voltage terminal 61 > 9 V) or "terminal 61 LOW" (alternator not working properly) on the CAN-interior.

Engine speed

The pulses from the crankshaft position sensor (engine 113, 156, 629 only) or from the crankshaft Hall sensor (engine 272, 273, 642 only) are read in by the ME-SFI [ME] control unit or by the CDI control unit.

The control units place the message motor speed (in rpm) on the CAN engine compartment. The instrument cluster receives these messages and evaluates them.

Alternator monitor, tml. 61 (= D+)

The CAN message "term. 61" can have the status "high" and "low". This status depends on the effective voltage at the input of the front SAM control unit. 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

The excitation winding is supplied with excitation current through a resistor located in the wiring harness. When "Terminal 15R ON", the voltage at "Terminal 61" is small since the excitation winding almost short circuits the voltage.

If, when the engine is running, the alternator voltage rises above the battery voltage, the excitation winding is supplied with current by the alternator. The voltage at "Terminal 61" increases to the alternator voltage.

The battery charge/alternator check function is closely linked to the lamp test and engine running detection ("terminal 61e").

Instrument cluster illumination, function

GF54.30-P-2007GZ