My 340 diesel doesn't charge the battery. I checked with multimeter, iddling, the voltage on alternator is only slightly higher than at the battery (12.0 volts on battery means around 12.05 on alternator). Rising engine revolutions, voltage rise by 0.1 V. If I unplug the thick red cable (heading to + pole of battery) from alternator, the voltage on alternator increase to 13.8 V iddling and to 14.5 V in high engine speed. If the cable is disconected, the pilot light is shining, but when is connected, the light indices everything is allright, however after hundred kilometers car stops with empty battery.

Hiya, I would reckon you're alternator is worn out, because if you unplug it from the battery whilst running you would expect the voltage to spike and destroy the voltage regulator, so I would say you should look at getting another alternator.

I had similar problem with my Bosch alternator, reason of fault was metal clip that connects internals of alternator to coal unit (brushes? need more words ), that metal clip was broken.

I would check that there is enough those coal (brushes?) left first.

Yeah, you are right Jani, brushes is the word. Are the brushes user servicable (ok, anything is user serviceable... are they supposed to be user serviceable) or is that time to get a new alternator?

On my 87' 360 B200K the brushes are fitted on the voltage regulator, that is it mounted with 2 screws on the alternator. I know some older models had the voltage regulator separately mounted another place, but its sure worth a check.