Hello,
I have a 1986 340 and recently the red battery light has been coming on intermittently. It might go OK for a a few days and then the light will come on for a while then go off again. It seems more likely to come on when the engine warms up. Does anyone know what this indicates? Is it that the alternator is on the way out? or maybe it's just that the brushes need replacing? or Could be some other minor fault?
I'd be grateful for any help. Many thanks. J.

I'd start with checking the alternator drive belt tension, voltage regulator (if you can replace these separately?) and then the alternator itself

Hi mate.
I recon steve has got it right. These altonators are now realy old.
When my red light came on it was the voltage regulater.
Hope this helps.
Cheers Mark.

Thanks for the help.
I think that the voltage regulator is built in.
If so, what's the best way to replace it?
There are screws and black plastic plate on the end of the alternator - it is an easy job to replace the regulator this way (and maybe do the brushes too)? What about the option of just putting an external voltage regulator outside the unit - like really old cars have? Would that do the trick?
Looking forward to hear your advice. Many thanks.
J.