C5 X7 Alternator Issue

[drumvlado]

Hi. I had a similar issue, but under other circumstances (upgrade of BSI), but the behavior was exactly the same.
This alternator should be set in the BSI as "2-nd generation controlled alternator", but there is also a setting "Type of non-controlled alternator" which, logically should not affect anything since this one is controlled, but it turns out that this is not the case and it should be set to "Control via line L".
The explanation is that when you start the car, the BSI assumes alternator is not controlled and uses this setting until all the LIN communication is started and then it start controlling it. See if this will help.

[xf1ref]

I had a similar issue last year and I was getting the error "battery charge or electrical supply faulty". I changed the BMS from the negative pole of the battery but that error was still there even if the battery was charging. Tracing the wires from BMS, I found in the fuse/BSI box that there is a 5A fuse and surprise, that fuse was broken due to corrosion. Replacing that 5A fuse solved the issue.