Hi, made a little progress on this. Still brake lights on until battery disconnected, also headlights. When I start up, there is a long delay before electrics 'kick in' and light warnings, indicators and wipers operate. All pointing to the CECM in the plenum? chamber under the bonnet, and or the wiring through into the driver's side, where the water was coming in. So it all stacks up. The guy who started the fix lost his mum a couple of weeks ago which is why this is dragging on cos I've no idea on testing electrics and still driving with brake lights on. I've already part broken the CECM casing lid trying to prise it off without removing the wipers and scuttle adjacent to windscreen...Derr!
Anyway,my mistakes might help someone out there. Don't know how long my mate will be out of action, so any help or confirmation that I'm on the right track would be much appreciated. B6 2002 tdi Avant.
(are the lights on fuses? I've tried pulling them one by one, didn't seem to affect the brake lights, so I don't know if ordinary tail lights are working, and I HAVE replaced the brake light switch on the pedal to no effect.)