Alternator Wiring Help

[Superman]

Here is what I know about alternator wiring: If you get it wrong, then wires fry. I hope to get it right. Here are two pics and here is my belief: The fat red wires go on the "+" side (upper left). The tiny blue wire goes on the "-" side (top right), next to the matching blue wire which is part of the alternator. The brown wires go to the lower terminal which, similar to the blue wire, is also on the plate marked "-". Correct?

[Leebag]

I just did mine few weeks ago. Here’s a picture of my old one from 83 sc when I pulled it out.

[RSTarga]

Don't forget the ground strap.

[ChrisHoover]

The pixies inside don’t care about the color on the outside. If it were me I would verify with an Ohm meter the terminals were connected to each other correctly regardless of color. There are some good wiring discussions on this board with diagrams.

[Superman]

Originally Posted by Leebag

I just did mine few weeks ago. Here’s a picture of my old one from 83 sc when I pulled it out.

Okay, now I need expert help. I (think I) hooked this alternator up the way Leebag did, and the way this diagram shows. Two problems: The alternator light is on and the system is not charging. What can be wrong. Can I reverse the smaller wires (not the fat red ones which are on the + buss) which are on the negative ( - ) 'buss' and perhaps that is the problem?

It is possible the wires may have gotten crossed during this project (wrong wires temporarily connected to the poles), but there are no burnt wires and there was no burning plastic smell at any time.

[al lkosmal]

Did you read the note regarding the resistor addition ....if the charge light doesn't go out?

[Superman]

Update: False alarm. In installation, I had pinched a wire against the alternator body, grounding it. The diodes and voltage regulator survived. I found a very good alternator/starter repair shop in Ruston (part of Tacoma) very close to the ferry dock. Couple of old fellows with REALLY good attitudes. Sound Starter and Alternator Repair. I said I may bring my spare starter to them. They said okay, but also that these old Bosch starters are very well made and do not often need rebuilding. I suppose they also need to understand these old 911s tend to have several hundred thousand miles on their clocks.

[Walter_Middie]

Sup,

I'm glad you found a real alt/starter repair shop. The good ones seem to be disappearing. There used to be one up here in the North end - Lynnwood Auto Electric. The old guy there used to have a shop either close to or next to where John Walker was working at the time, and remembered him. When I was working on my 911 alternator, I took it there. I set the alternator on his desk, and said Porsche 911 - no hesitation . He took me upstairs while he tested the alternator. His workshop was right out of a Boris Karloff movie of Frankenstein. Crazy electrical panels of dials and switches - but he fixed my alternator. I'm not sure what I would do now (Lynnwood Auto Electric is long gone). Maybe I'd go to Ruston and check out your repair place.

[manbridge 74]

Usually a quick process of elimination on three wire alts.

Red to large terminal
Blue to post with insulated washer
Ground to last one left
Also ground alt to engine case