14.3v engine running. Over 2 mins at about 1000 revs. Low fluctuation.
Nothing wrong there, unless voltage drops excessively under load.
The warning light is connected between an ignition switch output and the alternator field circuit, D+ connection.
On first switching the ignition, before starting the engine the light illuminates because there is no output from the alternator. The small current passing from the battery via the ignition switch providee an initial excitation current for the alternator field.
When the engine is started, the alternator is generating the alternator and battery voltages will normally be equal. No current flows through the bulb, and it goes out.
If when running there is a poor connection between the battery and the ignition switch, voltage may be lost on the way to the ignition switch, when cooling fans etc, which share part of the circuit are in use. This makes the voltage at the ignition switch lower than that at D+. In this case current will flow from D+, through the warning light towards the battery. If the voltage difference, and hence the current is sufficient the bulb will glow.
I am attaching a diagram "x230 Starting and Charging". Original is German, but I have added English translations.
Pay particular attention to the connecting point labelled "BB10" at the lhs of the diagram. On my Talbot Express which was the earlier 280 model this connection point was a 4 way large 9mm? blade connector. As I remember everything other than the main starter motor connection was routed through it.
For safety, disconnect the battery negative before investigating. Also worth checking the main chassis earth connection in front of RHS engine mounting.
For 4 way blade connector see photo. It was to the right and behind the blue glow plug controller. Your x230 may be different.
