74 Alternator/regulator issue

[ARCSinAK]

Hi-

Hoping for some advice on my charging issues.

Conditions: 74 911 currently has a alternator with external regulator. I installed a new Hella replacement regulator a 4 years ago.

Issues:

12.5 volt at battery when running no change as RPM increase.
Minor tow job couple night ago.
Had battery tested at Napa- checked out good


I have a spare alternator from a 76 currently bolted in a matching 5R fan housing so I am assuming it will fit. I ran into fitment issues in the past due to depth on my 80SC when I bought a replacement. Back to the point. The spare 76 alternator has an internal regulator. I read the porsche update in regard to how to make the switch but my 74 is bit of bastard child and the wires color do not match. See photo. White wire? The current alternator as the B+ red connection D- blue and 2 pins for DF. On my harness, I had the black and white, well the white has a short green jumper on it, connected to those two pins . There is also a ground from case that was connected to a bolt on the air guide.

At this point I'm not sure if I have an alternator or regulator issue but I have a spare 76 alternator with an internal reg that I could instal to eliminate/determine if the alternator is the problem and a spare regulator on order. Napa is informing me they don't have a cross reference part number for the alternator so they can't bench test it. Island life can't just run down to the alternator re-build store.

The spare alternator with in internal reg it still connected to the harness, see photo, with the following connections, 3 brown wires grounds, red and blue .


My question, is it possible to hook up this spare with the wires I have and eliminate the regulator. What happens with the current regulator wires?

76 Spare:


74 Existing wires



Regulator


74 Alternator

[gomezoneill]

I can see green oxidation at the main terminal fix that first. Then make sure all your grounds are good and clean (very important). Take your alternator to a advanced auto parts store and have it tested. My bet it's the grounds especially the trans ground strap.