Hi All (first post )

I've had a number of VWs. Currently own a B5 Passat 2003, 2014 GTI Perf7 and a T4 van.

So, I think I fried the alternator on the Passat due to reverse polarity on a jump start (don't ask).

I have VAG COM and it's not showing any codes, however the battery is not charging.

I used a donor battery and get 13.17v on start-up but then after a minute of so it drops to about 12.3V.

I would like to check the alternator blue exciter wire next but not sure if there is an easy way to get to it. Do I need to take the plastic fairing off underneath, or can I access the wire somewhere easier on the bulkhead, etc? I want to check this blue wire before I start thinking about replacing the alternator.