So here's the deal, I have a 1988 7.3 IDI F-350 dually. I completely redid most of the electrical as the person I bought it from had two different size batteries in the truck, had used scotch locks to tap into wire harnesses and had a million wires going to Nowhere under the dash. Needless to say I gutted about 2 floorboards worth of wires out of the thing. They also had installed I believe what was a 75 amp alternator. After getting rid of the excess wires I put in a leece Neville 165amp alternator and did the 3-g upgrade along with cleaning all my grounds off and putting fresh wires in there. Brand new electrical system completely as far as battery charging goes. I also left the factory voltmeter as it was because it is a couple digits off from the aftermarket gauge I installed that Taps directly to the alternator. That way I can see when the alternator kicks on and off and what the alternator is reading instead of running through a different system. Normally it kicks on and kicks off whenever I turn the truck on and off. Today I shut the truck off and was sitting there for a minute and my gauge light kicked back on for the aftermarket one which doesn't happen unless the trucks running and the alternator is started. It read about 10 to 12 volts and when I started the truck again it was up to about 15 or 16. It's an internally regulated alternator and everything has been fine with it for about 7 months now. Any ideas? I don't want to drive it around overcharging things and making things worse. I'm currently at a job site so I need to figure it out while I'm here. Much thanks in advance. It has also been raining everyday for about 2 weeks now. I'm not sure if there could possibly be moisture buildup in the alternator but finally the gauge went off after starting in a couple of times and turning it off.

 

What do you mean by "the gauge went off"?

The alternator shouldn't be turning on-off while the engine is running, it should be maintaining a fairly stable voltage.

 

My alternator kicks on and off according to my engine running or not. When i turn the truck off, a few seconds later the gauge with kick back on as if the alternator was turning back on again. Since its internally regulated I have it running to the gauge as well as the lights lighting the gauge. The gauge only lights up when the alternator is on so the alternator was kicking back on without the motor running and doing about 10 to 12 volts. It's still under warranty so I'm going to swap it out and see if that fixes it

 

What wire did you use off the old voltage regulator to power the new alternator? It should be the green wire. Also you referenced a 3G alternator and that is a completely different alternator than a Leece Neville

 

by 3-g I meant the extra grounds that you add to it. As far as voltage regulator to my knowledge it didn't have one. I assumed it was internally regulated as well. As far as wiring goes the only power wire I have is from the alternator to the battery and the power wire going to the new gauge. Other than that I have no extra power wires going anywhere

 

That leece neville should only require a key on power wire to the regulator, disconnect it and check both sides when it kicks back on after you shut it off,

I'm going to probably go with your regulator has an internal short

 

That was my thought as well about it having a short. I got the new one sitting in my passenger seat but if you live in Knoxville Tennessee you'll know it's hard to get around town cuz everything's flooded LOL

 

The fact that it's overcharging also points to the regulator. Post back once you've changed it

 

well I put one alternator in there that I exchanged mine for since it was under warranty and still nothing. I thought maybe the alternator was bad so I went back to the store again I swapped it out again and still the same thing. I'm not really sure what it can be since there's only one wire for power. I had everything up the same way and nothing is different it's the same brand and same type of alternator. I'm really confused at this point. Surely not all three alternators are bad. Does it have to kick on after so long? If the batteries are full is it just going to stay off? And also am I able to adjust it somehow? There's a plastic screw in the top. Does it possibly need to go a certain RPM before it kicks in? My other one just kicked on when I turn the truck on.

 

The truck had a external regulator, so you are feeding it constantly 12v instead of switched 12v power. You need to address that.

 

so even though it switched on and off as per the ignition its still getting 12v? I thought back to when i got it and yes your right it did have the grey box external regulator on the passenger side but it has since been removed. Im just stumped since its ran fine for almost a year without incident and now it has nothing. At least with the alternator I had in there it was turning on and showing something. Now it's just showing nothing.

 

I was sitting there looking at the wires and I remembered that I segregated a red and green wire or rather green wire with a red stripe. Which one does that go to? I remember reading somewhere that it wasn't necessary with a single wire alternator.

 

The green with red stripe is the power wire that should be going to the alternator and provide it with the switched power.

 

i remember that i seperated that wire because everytime i hooked it up to the power my battery light would stay on even with the truck off

 

optikal illushun what am i missing here? I thought i followed your post pretty well but have an internally regulated alt without the 3 wire harness.