You should be able to follow the red D+ wire back through connector C51 terminal 4 and connector C2 terminal 22 (from earlier diagram) to find the open circuit between the D+ wire on the alternator and the bulb.

 

Ok see if i can figure it out. Admit I'm not good diagnosing electrical. thanks for your help & patience.

 

think you're on the right diagnostic track Stellar, but one thing i don't understand is... you made a jumper between the battery and alternator D+ connector, started engine, connected jumper
and alternator began charging as it should. you then said you disconnected the jumper (with engine still running?) and alternator was no longer charging. if that's the case i believe that shouldn't happen.
the alternator should continue to charge until the engine is shut off.

this link also gives some insight into a jumper wire

https://www.volvoclub.org.uk/faq/Ele...torNotCharging

 

Are these right ones?

 

goodness .. i wouldn't even touch those.... those do seem to be the connections in hoonk's posted diagram though.

 

Source
https://www.volvoclub.org.uk/faq/Ele...torNotCharging

 

Back on the Road. I learned alot about charging system THANKS Everybody