2006 Electrical Fault When Hot

[forred22]

Hi.
My new to me 2006 955i has a major electrical problem when it's hot.
I put a meter across the battery and with ignition off its 12.5 volts.
Turn on ignition and the voltage starts to drop rapidly to 7 volts. This is not when trying to start it.
When it's cold it's fine.
I've checked earths
Charging circuit is fine.
Do you think it's a wire shorting to earth when hot?
Where on earth do you start?
Thanks

[Lee337]

Does it sound sweet when running?

I know some electrical components Cranbrook down when hot, such as coils.

P.s. welcome to the mad House 

[London_Phil]

How old is the battery?

[forred22]

Battery is brand new and the bike runs perfect.

[London_Phil]

There is a whole sub category on Girly charging here. I suggest you start there, as it may well be relevant.

https://tigertriple.com/forum/index.php/board,58.0.html

Keep us posted.

[Sin_Tiger]

This is likely one of these cases where you have to work your way through from first principles.

Clip a meter on volts across the battery. Ignition off.
Pull one fuse, switch ignition on.
Note voltage, switch off.
Repeat on each fused circuit.

If it drops on all circuits other than on the main 30A, then it's time to look closer at the charging side.

[forred22]

I've tried the fuse idea. got the volt drop after pulling each fuse. which is confusing. also unplugged charging system, so its not that either. must be something that is fed by the main fuse ??

[Sin_Tiger]

I think you're on the right track then 

[Bixxer Bob]

My first thought was a stator coil leaking to ground when it got hot but you say touve disconnected them and it still happens.

Since the drop occurs after turning the ign on, everything is OK as far as the ign lock. Assuming all the lights etc work OK you can forget those circuits for now. That leaves the feed to the indicator relay. Again, if they still work when it's hot its probably not that, but connection also feeds the  horn and rear brake light so that's a good place to start.  If they're OK, the next likely for me is the red/white going orange to the alarm connection under the seat tail.

Edit; when you say hot, is it hot enough to bring in the fan? If the fan is seized or sluggish that would do it.