Alternator Problem

[Sharkmatt]

Hi All,

This is my first post but I've already picked up a ton of information from this forum so thanks for that.  I have a 2005 Berlingo Multispace with the 2.0 HDI engine.  A little bit of history: the car had the common airbag warning light issue which I managed to fix with some great information from a post on this forum and a lot of frustration.  It turned out to be a combination of a break on the red/white twisted pair that runs under the scuttle plate and a dodgy pin connection at the plug in the engine bay fuse box.  I put the car through an mot shortly after fixing that issue but on the way back from the mot staton, the battery warning light came on!  I drove it home and did a few quick checks to establish basic faults.

- Battery check showed the battery was good which I knew anyway as I'd recently replaced it with a new one.
- Voltage drop test on alternator body to negative connection and alternator post to positive connection showed no issues.
- removed, cleaned and reinstalled alternator post connection.
- checked voltage at battery and was showing 12.2v with engine running.
- checked voltage at alternator post with engine running and showed battery voltage.
- checked voltage at purple exciter wire connector with ignition on but not running and showed 0 volts.
- checked belt tightness and pulley bearing with no issues.

The lack of 12v on the exciter wire jumped out as an issue so I tried running a jumper wire direct from the battery to the altenator connector to trick the alternator into starting but this didn't work.

The other unusual symptom is that after the first time the battery warning light came on, it has not come on while running again.  It lights up as it should when the ignition is turned to position 1 so I know the bulb works but it turns off when the engine starts even though the alternator is not charging.

I'm a bit stuck at this point because the lack of 12v to the exciter wire seems to suggest a wiring/bsi issue but that means the alternator should kick in with a 12v jumper and it doesn't.

Any ideas where to go from here?  I don't want to replace the alternator if it's a wiring/bsi issue.

Cheers, Matt.