Getting ready to replace the positive and negative battery cables on my '72 Supreme and in the process I'm going install the alternator cable cap. I see they're available in both red and black...how do I know which one I need?

 

For the alternator cap, I’d go red.

It is the positive output from the alt, so red would be appropriate to stick with the factory color coding of red=positive; black=negative

 

I agree with that logic, and my first choice is red, but why is black even an option? Makes no sense to me.

 

Maybe the caps are just basic generic caps which fit many applications & not simply alternators? I don't know. I know you if were to purchase an alternator for a Nash, Packard, Studebaker (some others including many older European vehicles) you'd be looking at a positive ground system instead of a negative ground system.

 

If I remember correctly the Red is for the OEM high (63 amps-Convertible) Alternator and Black is for the OEM Low (27ish amps) Alternator
I think this is noted in the Assembly Manual (at work so I cant check) I think that is how I figured out which one to use when I replaced my Alternator (Old one was red also)

 

You won't find an alternator listed in the Assembly Manual because the device you're referring to is a Generator.

 

I stand corrected it is listed as a Generator not an Alternator, and I looked again and it doesn't state a cap color
I know I saw it somewhere but for the life of me I don't remember where
I guess if you are doing a show car and looking for points it would matter, otherwise I guess go with what you like

 

There is a black rubber alt positive terminal cover, and a hard plastic red cover.
I personally have not seen a hard plastic black one.
Steve

 

Pretty certain the ASM lists only a red cap & I thought they were all OEM 63amp? I never thought there was delta between convertibles & others as you suggested. Maybe so.

 

They don't list the color of the Nut Cover - only the color of the (red) wire.

 

My car is hours away, and I haven't worked on it for a while. But I think my 69 has a black cap. I think Pontiacs used red caps. I think the plastic washer that the cap snaps on to, is the color the cap should be. That's just from memory, and I could be wrong.

 

Mine is a hard black plastic cap from the factory.

 

Mine is also black, from the factory. My 1969 GMC has a black rubber cap on a 100 amp. alternator.

 

There is a chart in the Service manual that shows Generator amp Rating based on specific options in the vehicle, Base 37 amps, (IIRC) Rear defogger 61 amps and Convertible 63 amps, maybe one more in there

 

That's good information. Thanks.