NEW Alternator - Bosch(!) or Valeo?

[911 envy]

911 Envy again

I have a followup question. I’m replacing my alternator because all the suggested trouble shooting meter readings indicated regulator was fine but alternator yielded weak readings. I thought I had checked all grounds and connections but when I was removing alternator I could not find a ground leading from the block to the to the shroud through the diffuser bolt. Then when I pulled the diffuser I discovered a shot wire broken off on one end and twisted open wire oh the other. Wire is just long enough to reach from the diffuser to the block. But I don’t see any evidence of a broken wire on a block bolt or nut.

So now I’m wondering if I really need to buy the new alternator?

[PeteKz]

The original installation had a thick brown wire from the ground post of the alternator to one of the case studs/nuts. It's good to have, but it's redundant. The alternator also is grounded to the fan housing via the 6 studs that hold it into the housing. The housing in turn is grounded to the engine. All of these points can develop corrosion, and increase the resistance from the alternator to the engine case, which is why Porsche installed the brown ground wire too.

I would retest the alternator output with a ground wire connected to it just to be sure that it still tests bad, but given the other paths to ground, I'll be surprised if that's the case.

[917_Langheck]

And that is just the ground from alty to engine. Then the ground from engine to chassis has to be good, and then from chassis to battery.

Lots of places to float your ground, and get caught in a loop of who's on first....?

[911 envy]

All this makes sense to me. I cleaned all the other grounds mentioned and they seemed good before I even cleaned them. I already purchased a new alternator so I’m going to install it. May have my old one rebuilt if it seems to be a good candidate. Will keep my external voltage regulator close by.

Thanks for your help.