Hey, i have a 1973 f100 that ive been working on lately. I had a bunch of issues with it just dying in the middle of a drive. One of my recent upgrades was a nice stereo, so i eventually realized that my alternator couldn't run the truck and the radio, i just bought the powermaster 140 amp, one wire alternator from summit racing and it fits perfectly, i hooked up the batt wire and ground like the instructions say. When i go to turn the key, nothing. After a little research and messing around i got the truck to start by bumping the starter relay if i hook up another wire from a prong on the alt to a wire on the voltage regulator. now it will run and charge, the key will turn the truck off but not on, so i have to bump the starter again, i cant figure out why, or what else to connect this extra alt wire to in order to get the ignition right. Let me hear any thoughts you have. Thanks, Asa

 

Did you blow a fuse?

 

Did you disconnect any wires from the solenoid when you ran the wiring for the new alternator?

 

i disconected one of the old alt wires cause i didnt need it anymore. and i dont think i blew a fuse since i still have to have the key in the on position to bump start the car, but ill check in the morning

 

Check this tread out. Sounds similar to what you have. In particular, the three wire plug that has the black/yellow wire.
https://www.ford-trucks.com/forums/1...r-problem.html

 

And what about other stuff? Do you have any power to the cab at all?
It's kind of strange that it was running. Normally after you get the starter cranking, the alternator can keep the engine running. But I'm not sure where the ignition was getting it's power from.

Without that Black w/yellow wire nothing gets power. Since the engine was running, sounds like it's intact.
Unless the relay is defective and was sending power up the Brown "I" wire, but then the key would not have turned the engine off.
Strange...

Got dual batteries?
Got pics?

Paul

 

Hmm, is that the Green w/red wire from the OLD regulator you're talking about?
If so that is probably where the ignition is getting power fed to it. It feeds back from the alternator to the ignition switch, then out to the ignition coil.
Maybe...

Still like to see pics, but it's fun trying to figure that stuff out in your head sometimes. So I just had to throw that out there.

Paul

 

As has been mentioned before. Pic's would help to what you did etc....

I've done the 3g conversion with no issues. The first time I did it I disconnected the wire that sends power to the cab. Took me a few minutes to figure out what I did wrong.

 

Good questions, 1Ton. I have installed the 1Wire unit and love it. My recommendation to those that go with this alternator (or anything that would be an extensive add-on) is to get a dual post battery. The one with both types of battery posts (pos and neg) on it. This accomplishes two things:
1) Ease of installation. The alternator wire can go directly to the battery without disturbing the other wires at the solenoid.
2) Making a more solid connection. The solenoid post can only hold so many connectors before it won't have enough threads to hold tight.

 

just got home and connected the black wire back to the starter solenoid and everything works like normal, what i cant work out is what to do with the other end of that black cable that used to hook up to the alt, now its a hot wire floating around, can i just cap it off?

 

 

Hey, great news. Glad it's working.
But it would still be nice to see a pic of all this. I don't know why you'd have the additional hot wire still intact. On my truck, it was a single wire between the alternator and the starter relay, and a separate wire from the relay to the driver's side firewall "power stud" mounted to the body before the wire runs into the cab. I'm pretty sure earlier trucks had a different routing, but I don't know what you're dealing with until I see it.
In other words, why can't you just remove the entire unused wire?

But basically, yes you can cap off the wire to keep it and the rest of the wiring safe. But it has to be a very robust, safe and permanent kind of fix. One that is not going to pop off someday while you're out wheeling for firewood in the jungles of South America and catch your truck on fire.
Which is why it's better to be able to remove it entirely if you can. If you really can't, then make it safe.

Not sure if this is workable for you or not, but what I've done with many trucks that have to modify this is to convert the old unused wire to a power source. For this I get an insulated stud and connect the wire to the stud. Now you have a pretty high-amperage capable power supply. A friend just posted a pic of one possible version over on classicbroncos. I'll go hijack it and post it up for you here in case you're not familiar.

But a cell phone pic would still be a cool thing.

Paul

 

Here's a handy junkyard one, common on old '73-'87 GM trucks. Some come with a metal buss (jumper) between the two studs, some are separate. I've used them mostly independent of each other, with the larger one for the Black wire and always hot. The smaller one I connect the old Green w/red regulator wire for use on switched circuits.