Alternator wiring

[James Petty]

Hi,

I was fortunate enough to buy a 911SC with the Classic Retrofit Aircon a few years ago.  I noticed that the alternator light in the dash never worked but figured I would hear it if the belt failed.

Last weekend I removed the fan and housing to get them cerakoted and took my first look at the wiring on the back of the alternator.  Mine has the red and brown wires in the right place, but there is a black wire to where the dash light wire should go and the blue dash light wire was insulated and was connected to nothing.  This might explain why my light doesn't work, but I'm assuming that it was deliberately wired that way. 

From the wiring diagram it seems like the black goes to the voltage regulator, the Classic Retrofit alternator is internally regulated, so is the black wire needed?

Any suggestions from the forum?

[classicretrofit]

Hi James, the black wire is discussed here, with further info from a Porsche TB:

Does this help with your question?

[James Petty]

Hi TB,

Just closing out on this.  I dug into the operation of the alternator and figured that the black connection was feedback from the external regulator.  I was worried that I might fry the alternator if I did some incorrect connections.  I also checked that the external regulator was disconnected, and it was.

I put the green wire on the right connector and left the black wire off (insulated).  And when I put the Alternator back in the charge light worked correctly.  So I’m not sure what the guy who installed the alternator was thinking.

Thank you for your guidance.

Regards, James