Battery Charge/Alternator Check, Function

Battery Charge/Alternator Check, Function







- Message: "BATTERY/ALTERNATOR VISIT WORKSHOP!"

Battery charge/alternator check
The message "BATTERY/ALTERNATOR - VISIT WORKSHOP" in the right multifunction display (A1p15) belongs to category 2. It appears when the alternator (G2) is not operating correctly (terminal 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:
- Terminal 61 alternator check
The signal "Terminal 61 (= D+)" from the alternator (G2). The alternator check terminal 61 signal is registered by the passenger-side SAM control module (N10/11). The passenger-side SAM control module (N10/11) then relays the message
"Terminal 61 High" (voltage at terminal 61 > 9 V) or "Terminal 61 Low" (alternator malfunction) onto the interior compartment CAN.

Engine speed
The ME-SFI control module (N3/10) registers the pulses from the crankshaft position sensor (L5). This control module relays the engine speed message (in rpm) onto the engine compartment CAN.

The instrument cluster (A1) receives these messages and evaluates them as described above.

Terminal 61 (= D+) alternator check
The CAN message "Terminal 61" can assume the states "High" and "Low". This state varies according to the actual voltage at the input of the passenger-side SAM control module (N10/11). It becomes "High" when this voltage exceeds 9 V. It becomes "Low" when the voltage drops back below 4.5 V.

Pre-excitation current for the alternator
The excitation winding is supplied with the pre-excitation current via a resistor located in the wiring harness. When the ignition is switched 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 by the alternator (G2). If the voltage at terminal 61 increases, the alternator voltage also rises.

NOTE: The "battery charge/alternator check" function is closely related to the "lamp check" and "engine running recognition" functions (terminal 61e).