Do we have any electrical system guru’s on here?

[767Jockey]

Of all the different areas of working on cars, electrical is by far my weakest, and number 2 on the list isn’t even close. Electrical is voodoo science to me. I know very little about it and I understand theory and troubleshooting even less.

That said, I just switched over to a Ford 3G alternator from the original 60 amp unit from the 60’s. The original unit had been converted to a one wire system a while back. It stopped working so I went to a modern 130 amp Ford 3G. I bought the alternator brand new, it’s a ACDelco Gold unit. The one I am using is from a 1996 Mustang with a 6 cylinder. After swapping the pulley to my old V belt and re-clocking the back putting the terminal locations in the proper position in relation to the mounting ears, it’s a direct bolt on, and it fits like a glove. The hookup is stone simple. I ran a heavy 6ga wire from the main output terminal on the alternator to the battery terminal on the starter solenoid. There are two plugs on the back of the alternator. The larger one has 3 wires coming out of it, the smaller is one single white wire. The directions I followed said to connect the white wire from the small plug to the white wire from the triple terminal. I did that, soldered and heat shrink wrapped it. There is a yellow wire that comes out of the triple plug, that goes back to the battery terminal on the solenoid as well. The last connection is the green wire from the triple plug. I ran that to the IGN terminal on the ignition switch. All connectins are soldered and covered with heat shrink sleeves. The drawing below is what I folloeed for directions. They're all good coonnections. I started he car and perfecto! I had a solid 13.8 volts…..until I didn’t.

Today I started the car and it’s not charging. I noticed the voltmeter in the car was low, and with the car running I measured back at the battery terminals with a VOM and got only 11.8 - 11.9 volts. All the connections outlined above were checked and re-checked. They’re all good. I took off the two main grounds on the car, cleaned and re-grounded them. All good. I took the alternator to two different auto parts stores to spin up in their machine to check it. Both said it checked out just fine. The fan belt is plenty tight. I checked the mega fuse in the main charging line off the alternator. It's intact and fine.

At the same time I also have a problem with my electric fuel pump. It’s struggling to run, binding, surging, sputtering and moaning. It’s shot. I have a new fuel pump arriving here in a couple of days. Could the draw on this bad pump be so high that it’s messing up the charging system somehow? If it matters, my car has a Ron Francis Factory 5 Cobra harness. It’s not a Factory 5 car (it’s a Contemporary) but the harness worked out well. The fuel pump relay is on the fuse panel. Could something wonky be going on with the fuel pump relay to cause this charging issue? I know I’m grasping at straws but how all his works together is a mystery to me.

Also, I have read that some guys attach the wire that runs from the alternator to the ignition switch to the ACC terminal on the ignition switch instead of the IGN terminal as I have it hooked up now. Could this be an issue? It did work before like this however. Maybe the IGN terminal isn’t supplying the proper signal to the alternator to wake up and do its thing?

Maybe the alternator stops charging when it gets hot? I don’t know how you’d check that other than letting it cool off and see if it works again. I can’t try that right now, it’s past 11PM here and this thing is LOUD.

A friend of mine is trying to assist long distance but I hate to keep bothering him (sorry Jon!) If anyone has any ideas on where to look further I would greatly appreciate the input. Thanks!