Alternator not charging, no D+ voltage

Hello,

i have a charging problem on my M5. Light is on, nothing on the D+ blue wire...

I bought a new Bosch alternator -> same problem, i changed the K61 unloader relay -> same problem!! The alternator give 14 volts throught the D+ and to the battery only when i rev the engine at around 5000rpm, after it stay at 14 volts BUT if i stop the engine then start, i have nothing again...to finish i must tell you than even when i have 14 volts the charge light is always on....

Does anybody knows were the UNCOUPLING DIODE is located? Or any other idea?

Thanks for your help.

Alternator not charging, no D+ voltage