So en I baught the truck, the alternator harness was hacked to hell. Managed to find a good on. Got all the connections tested with my multimeter and everything seems good. Got it cleaned up.
The problem, is putting it on the alternator. Part of the hacking involved getting a different alternator than was original. I have the original and im scared to death im gonna put the connections on wrong. Ive done some research. Below is a piece of my shop manual, showing where the wires hook up. Also is a picture of my harness with everything layed out. From what I am gathering the
1. Black/Red wire goes to the 'Battery' post.
2. Orange wire goes to the 'Feild' (?) post.
3. the White/Black wire goes to the 'STA' (?) post.
4. I am going to run a ground wire to somewhere from the 'GRD' post just to be on the safe side.


Like I said, im scared to death of putting something on wrong and setting my truck on fire. So I wanna make sure I do good work right the first time. I may be simply asking for confirmation of my research, but I would rather look like a fool and do it right than do the work wrong. Thank as always for reading.

 

This is the screen shot of my shop manual im referencing

 

This is my layed out harness

 

this is my intended layout

 

Is that a 1978 harness with gauges? It looks good to me, the large black/red to the BAT, the white/black to the STA and the orange to the FLD. At the top of the harness, the Red and Yellow/Black are your Amp gauge feeds.

 

I have seen many threads on 3G heavier duty alternators here - that may be what the hacked-up harness and 'different' alternator were? I would search the threads to determine if that could be the case - you may want to repair the harness to accommodate that alternator instead of getting a period-correct replacement installed.

 

perfect time to do a 3G alternator swap.

Looks cleaner under the hood, eliminates the external regulator and a lot of the wiring, easy to wire in, plus it puts out 130 Amps. I ordered my 3G alternator last night.

 

You have the wires hooked up correctly in your picture.
In the factory harness, there are four wires in the harness but you only see three. The factory ground in the harness is the small tab that connects the rubber strain relief to the alternator. If you were to cut the strain relief open, you would see the ground wire is soldered to the tab to make the ground connection.

 

Mike, you lost me? im missing a wire?....theres none left unaccounted for?


and a 3g swap might happen. But I want to know that im starting with the right stuff before I cross that bridge

 

Yeah, you're missing the factory ground connection. A PO (one of the worst things that can happen to our trucks, btw) probably got rid of it when they butchered the harness.
In your illustration the harness has a rubber strain relief that is attached to the alternator by a small metal tab. This tab is the actual ground connection for the harness. The other end of the wire that is attached to the tab goes to the top mounting screw of the voltage regulator.
Basically it goes where you were talking about in your first post.
Here are some pictures that I took of mine. It was a NOS part but was made incorrectly. One wire was made too short so I had to cut the strain relief open to repair it.

 

Thanks a ton mike for the pictures. I greatly appreciate it.

 

Good Pics all!!!!

 

I'm digging up an older post here, but I think I have been having exactly this issue and I'm hoping someone can help me a bit. I have been having electrical issues ongoing for a while in my '79 F250 with a transplanted '70 Lincoln 429. The most obvious symptom is that the battery is not charging (checked with a multi-meter as well). The battery runs down while driving (multiple other issues as well).


I have had my battery tested and it checks out - holds 12.7 volts (checked today with a multi-meter). The alternator had gone bad and was replaced. Looking at the pictures above I do not have a strain relief on the harness and I see no ground at all from the alternator. There are two wires coming off the STA connection, but as I understand this is a signal wire(s).

It seems clear that I need a ground to the alternator as indicated in the picture above. My question is whether I should just run a separate ground wire to the alternator and tie into the frame, or find a strain relief harness somewhere (anyone know where to find one?) and tie into one of the STA signal wires?

If anyone knows and can help I would much appreciate it.

 

You can run a separate ground wire from the alternator to ground without problems. My ground is the black wire with a yellow insulator ('79 250). I have to say I have an alternator from an E 350 - 130 amp....had to take it apart and clock the back side so the mounting holes would line up.

Does your wiring look like this?

 

Thanks Filthy Beast for the reply. I don't know how I have been running the truck without the ground to thew alt the six or so years I have owned the truck - though I have had all sorts of electrical issues the entire time.

No my wiring and alt look exactly like the set-up in post #10. I have to pull an engine from a Subaru today (yay), but I'll try to run that ground on Sunday and see what it does for the situation.

edit* I decided to rig a temp ground to the alt and I didn't see a jump in volts with the truck running indicating that the alt is charging, however, the ten minutes or so I ran the truck including a jot around the block it did not drop in volts - steady at about 12.5v

I'll have to do some actual driving around town and see if it drops after that.