Hey all. Been a while since I posted here, but search for answers quite often. I am doing the 3G alternator upgrade on my 77 crew and I purchased an aftermarket kit from PA Performance that comes with an updated voltage regulator so you can still activate the factory amp gauge on the dash (3rd picture below). The kit comes with the 3G alternator harness and the new voltage regulator. In looking at wiring, it's all pretty self explanatory. The plug for the old voltage regulator on the radiator support plugs into the new voltage regulator. The yellow wire on the new alternator harness loops around and attaches to the positive stud on the alternator along with the positive cable and fusible link that will run to the starter solenoid. Now, two questions. The vendor of the kit says that the green/red wire on the new harness needs to hook into the field wire off of the old alternator which is the larger red (or faded red) wire pictured below. I have read that the green red wire should go to the green red coming into the harness from the cab. This green/red wire goes into the voltage regulator plug shown in the 3rd pic. But, I guess these wires both run into the voltage regulator so maybe it's the same connection? So, does the field wire connection sound correct? My other question is, I have read that the big black wire (has a yellow tracer up the line) below with the eyelet on it should loop back and attach to the solenoid also. Is this right. Just seems like there's going to be a lot of wires left over but maybe that's because I'm still using the voltage regulator. Thanks in advance for any help

 

There is a issue with that kit, the charge wire! How do they expect you to keep the stock ammeter and stock charge wire working on the new 3g? The stock charge wire is barely adequate for a 40amp alternator and lacks and short protection. All that kit is is a dummy VR that accepts the stock harness the red wire out to field gets connected to their 3g pigtail. In the VR housing they tied the yellow, green/red and the red together for the 3g.

 

Thanks Gas Hog. Which one is the charge wire? I will be running a battery cable to the starter solenoid through a fusible link. Is that what you mean? What harness are you using?

 

Better cancel your fusible link idea, you need a 150amp mega fuse and holder. The charge wire is black with a yellow trace. This wire shouldn't be connected to the 3g alternator.

Here is a basic 3g kit or you can do your own version

 

Well that's what I mean. I have a 200 amp mega fuse and cable that I got off of Amazon. So you're saying the wires on the new harness aren't big enough? I've seen other guys using them?

 

The stock charge wire will burn up if used. It should never be used above 60amps.

 

3g is pretty simple only two wires going to truck are main charge wire - I went with a 2 gauge wire to solenoid through a 150 amp breaker & the green wire to ignition(?). the other two wires rout back into the alternator & everything else on truck isn't used. At least on mine.......

 

Thanks Traktor That's what I'm looking for. Did you run your green/red wire to the green red wire coming out of the old harness on the truck?

 

This might help. I downloaded this years back from who knows where.


I did have to use a double V belt pulley to keep it from squealing at take off. I used a 175amp mega fuse. You might have to 'clock' the alternator to get the wires exiting at the bottom out of view.

Here is what you lose:



FWIW, there's a great vid on youtube that shows how to rebuild the 3g alternator. After watching I'll never buy another rebuilt again.

 

Thanks F250 Restorer. I've seen that diagram a lot lately. Where did you hook your green wire into off the new harness? In the diagram it says to hook it to warning lamp or ignition switch.

 

The wires are the same colors, the 3g green w/red goes to the trucks green w/red that goes to the VR. Upstream this is feed either through the alternator light or off a low ohm resistor in ammeter equipped trucks.

 

Thank you. That's the answer I was looking for

 

He beat me to it. It's actually really simple but so much conflicting info makes it seem more complicated. Much of the info always on mods like this seems t come from people who haven't actually done it just read about it and have to chime in like they are experts. When I was finished I was almost surprised it worked because there wasn't more to it, lol. Made a huge difference especially when running my winch..........

 

Did you purchase an alternator also? And which engine?

 

Yeah, I hear ya on the expert part. Through some other research, it was pretty simple. I have it pretty much done already. I'll be adding an aftermarket amp gauge too