Battery Charge/Generator Check

Message: "BATTERY/GENERATOR CHECK - FIND A WORKSHOP"

Networking:

Battery charge and generator indicator
The message
"BATTERY/GENERATOR - FIND A WORKSHOP"
in the multifunction display (A1p13) replaces the familiar generator charge indicator lamp (A1e5).
It appears when the generator is not working correctly (terminal 61) but the engine speed is higher than 200 rpm.
If the engine is switched off there is no message

Networking
The following data is required:
- Terminal 61 generator indicator
The signal "terminal 61 (=D+)" from the generator (G2) is read in directly by the instrument cluster (A1).
- Engine speed
The pulses from the crankshaft position sensor (L5) are read in by the injection system control module (N3). This control module sends the message "engine speed" (in rpm) to the CAN/engine compartment.

Terminal 61 (=D+) generator indicator
The terminal 61 signal can assume "high" and "low" status. This status depends on the actual voltage at the input of the instrument cluster (A1). It is "high" if this voltage is higher than 9.7 V. It is "low" if the voltage drops below 9.4 volt again.

Pre-excitation current for the generator on vehicles with generator charge indicator lamp (A1e5) (standard wiring)
With standard wiring the generator (G2) receives the pre-excitation current via the generator charge indicator lamp (A1e5). When the ignition is "ON" the pre-excitation current flows from terminal 15 to ground via the lamp and the excitation winding. The voltage at terminal 61 to ground is small as the excitation winding almost short-circuits the voltage.
Almost the entire voltage drops at the lamp; the lamp is illuminated. If the generator voltage increases, and therefore also the voltage at terminal 61, above the battery voltage when the engine is running, the excitation winding is supplied directly by the generator and the lamp goes out.

Pre-excitation current for the generator on vehicles without generator charge indicator lamp (A1e5)
On vehicles without a generator charge indicator lamp (A1e5) the generator (G2) receives the pre- excitation current via the resistance R(suffix)v of the instrument cluster (A1). When the ignition is ON the pre-excitation current flows from terminal 15 to ground via the resistance R(suffix)v of the instrument cluster (A1) and the excitation winding of the generator. The voltage at terminal 61 to ground is so low that the excitation winding almost short-circuits the voltage.
If the generator voltage increases above the battery voltage when the engine is running, the excitation winding is supplied by the generator. The voltage at terminal 61 increases to the generator voltage. The respective voltage at terminal 61 is evaluated in the instrument cluster (A1) and the multifunction display (A1p13) is actuated as described above.


NOTE: This battery charge and generator indicator function is closely connected with the bulb test and engine running recognition functions (terminal 61e).


The specified voltage thresholds only apply at an electrical system voltage of 12 V. If the electrical system voltage is higher (e.g. 14 V) the thresholds are also higher.