I am curious if anyone else has noticed that on some 1965 (others also) that the delco alternator sometimes has a white cap or cover on the NEG post. The cap seems to be made of nylon and is seen on very original cars. Anyone have a source or a part number for this cap?

 

You mean the positive post? Most repro suppliers have them.
Heres one from OPGI:
https://www.opgi.com/cutlass/1969/ig...stems/C220090/
or this one:
https://www.opgi.com/cutlass/1969/ig...stems/CH20399/

 

NO. I mean the NEG post. I think they are a rare site and folks repairing the alt. just throw them. I have one on my 65 and I did see another this last weekend at a show. (also a low mileage original 65).

 

What, pray tell, is a negative post on an alternator?

Output is positive, negative is the frame of the machine.

 

Picture?

 

There are 2 stud posts on the back frame of the Delco alt. One is marked Batt. and the other GRD. for ground. (not marked negative). Sorry for the confusion but the delco was a negative ground unit on 60`s GM cars. Some of GM large cars actually had a wire to the GRD. terminal of the alternator unlike most GM "A" bodies.

 

I think its just there to either protect the post from damage or keeping the wires from chafing on it. I don't think its an electrical insulator.

 

I agree. It would not seem necessary to insulate the ground post. It may even help factory installers get the correct post. (The two studs are different dia however). And some one mentioned protection during shipping or installation damage to adjacent parts.
Surely someone out there has a delco parts book and can give us a part number.