Okay Gentlemen! I am getting my butt kicked!!! what I have is a 78 super cab f250 with a 12 valve cummins using the mopar alternator with a ford regulator and have been for 8 years with zero problems. the other day I ran to the store and while i was on my way there my radio kept going off and on as I was just in the dash replacing instrument lights thought must have knocked a connection lose,got to the store came out and I had nothing no ignition ,lights,nothing! so I zip tied the the fuel shutoff solenoid open and jumped the starter relay and got home.so I started looking into it a found the fuseable link from alternator burned and found a bare wire next to it thought okay must be it WRONG! I have put three voltage regulators and 2 alternators on it and have the same issue,now the reason I have done this is because i traced the problem circuit back to the ignition switch and the only thing I can disconnect that will stop this from happening is the green/red wire that goes to the voltage regulator. I have literally disconnect every thing that has power and hooked it back up one at a time along with the ignition switch until it started again and the only thing that make it get hot is when I hook up the regulator. I am completely stumped any help would be GREATLY APPRECIATED!

 

Need a picture of some of this. If not only to help diagnose your issue, but just to check out your cool install!
But the first thing that jumps out is, why does a Mopar alternator on a diesel even need a Ford regulator in the first place? Are we talking about the original fender mounted regulator from a '78?
Isn't the alternator an internally regulated version? What year is the engine from? Or I guess more to the point, what year is the alternator from? Anything from the mid to late seventies in some cases (mostly GM), or late eighties in most others, is going to be in internally regulated, stand-alone alternator that does not need to be connected to an external regulator.
They don't need two regulators. So maybe I'm missing something and your setup is using an older alternator?

Looking forward to pics. And to getting you back on the road reliably!

Paul

 

because the voltage reg on the dodge was built into the computer,thus when the regulator side of the ecm took a dump you had to buy an ecm. and yes original ford regulator

 

👍🏼 got it. Thanks for the explanation.
Didn’t know that!
only vehicle that I have worked on in recent years that had that same future, it was a jeep grand Cherokee.

 

not a 100 percent sure when they went internal but I think up to 01 they were regulated through the ecm. Just a side note for anyone doing this, you have three connectors on a dodge alternator they are basically top middle and bottom the top gets the orange wire from the voltage regulator the middle grounds to the case and the normal charge wire goes to the charge post and if you hook the top and middle up backwards they will make 24 volts! ask me how I know!! but I digress, I think I have it figured out.I was using almost 50 year old alternator harness, so out of desperation I pulled it all out and redid it all and now it is working! didn't really find anything to point my finger at for sure, But I did find some corrosion and some broken strands on the 5 factory splices.

 

Good detective work! Glad you've got it working again.
If it was visible at the main connector at the regulator (is yours a 3-wire, or 4-wire version?) you might see it as a voltage drop at either the Green w/red wire, or the Yellow (maybe Yellow w/white) wires.
The Yellow wire has to have full battery voltage at all times, and the Green w/red wire gets as close to battery voltage as reasonable, only with the key in the ON position.
Otherwise, the Orange wire just needs a good clean connection between the regulator and alternator.

And of course, no corroded/exposed strands allowed! Especially at splices!

Paul

 

thanks for your input paul I do appreciate it!!

 

Well here we go again!!!!!!!!!!!!! I am Totally lost here can not for the life of me figure this out! I pulled the original alt wiring harness out and redid it now it's just the charge wire going to the alternator with an 80 amp reset-able circuit breaker and all the other splice wires are together with a 30 amp circuit breaker they both go to the starter solenoid and again the only thing that will stop it from popping the 80 amp breaker is the green red wire being disconnected.Please help if you can.

 

Well, seems like your 80a breaker is undersized. Tell us again what year the engine (or more important, the alternator) is from? Is it a 70a alternator, or is it a more typical 100+ amp alternator. Some diesel applications have 200a alternators.
All you have to do is start that thing up with an even slightly low battery, and it's going to immediately try to re-charge it to the tune of at least 60 amps, if not more. Sounds an awful lot like the "more" scenario at play here.
When you disconnect the Green w/red wire, you stop the alternator from charging. Or, over-charging if that's the case. Did you measure output voltage while it was running by any chance? Did it work long enough before tripping the breaker?
When we build harnesses for Ford 3G upgrades with 130a alternators, we use 175a fuses! That's because even a lowly rebuild can often put out up to 150a when called upon to do so. Hence the overkill with the fuse protection.

You would think you are protecting the component (and ultimately, you are) but you are really protecting the wire/cable/conducctor. So what size is your main charge wire?
Was it a large battery cable sized one to begin with? Did you replace it with a larger one? At least 6ga, but hopefully larger if you don't know what your alternator output max is. We use 6ga for 130a alternators. If you're custom making one with a longer run, going to 4ga is not out of the question.
Is it overkill? Of course! But you're good when you overkill it just a bit at least. For me, with battery/starter cables, and alternator charge cables, overkill is just enough.
My point being, is if you have a modest length of 6ga cable (or even a short 8ga) then a 120a breaker is not out of the question. Nor is a 150, or even 175a breaker!
Depends on what you're using.

And what exactly did you re-do on the alternator wiring? Just the regulator? OR the main output wire too?

Paul

 

Paul you probably just answered the question it's 120 amp with an 80 amp breaker! 6gauge wire

 

Sounds like time for an upgrade! :-)
But because it’s tripping an 80 amp breaker, check the voltage right away the next time you fire it up. Make sure it’s not overcharging.
And maybe, if you happen to have a battery charger, put your battery on the charger overnight and let it do the bulk of the work ahead of time. That way your next startup of the engine won’t result in the alternator trying overly hard to recharge the battery.
A quick recharge of a charged battery that just started an engine (a gas engine) usually only ends up with 30 or 40 amp output for a few minutes.
Then again, this is a diesel after all! They usually put a strain on a single battery to get started initially. Maybe it’s normal for an alternator to output heavily right after the first fire up.
Would certainly explain tripping an 80a breaker.

 

Voltage is max 14.24 volts the highest I have seen it, took some where between 100 and 140 miles before it tripped and only after running the lights and it's dual batteries.thanks again Paul.

 

Perfect! Sounds like you’re there.