Dodge Ram Van alternator and regulator problems


I’m not sure if this is the place to air my problems, if not, please advise me what and where.

On a recent trip my 1991 Dodge Van camper van lost its alternator. Several stops at several shops were to no avail. The last stop, at a Dodge dealer, resulted in a new Nipponsendo 120 amp alternator wired up in a Mickey Mouse fashion just to get me back on the road. The alternator doesn?t have a built in voltage regulator, it is built into the computer module and cannot be replaced unless the whole module is replaced, which was 3 days away.

The tech guy ran a wire from the field ground screw to a switch I could control if the voltage went too high. It did at any speed over idle. I made it home in 2 days of interstate driving stopping every 1.5 hours to let it charge the battery up to 13.3 volts from the 11.9 volts it went down to while driving. If I was in stop and go city driving I would have had to stop just as soon and only go 25 miles and not 75.

The tech guy said the RV battery isolator was installed wrong and the Dodge alternator wiring was all changed. That is why he had to do the Mickey Mouse wiring.

After looking at my non factory manuals and my van?s wiring, I think I have figured out why and how the factory wiring was changed for the isolator, which has worked flawlessly since 1991. My question is, can a voltage regulator be installed in this new field ground wire to regulate the charge rate and bypass the old built in regulator? If so, how? And what kind? I would think that any regulator in this line would act like regulators do by the rapid on and off control of the field ground.

I have made diagrams of how Dodge did it originally, how the RV company did it, and how it is now. If these would help in answering I could send them to anyone via email attachment. I am at if it is necessary to reach me personally.

Thank you for taking the time to read this epistle, BobTom.


I can’t imagine why the prior owner messed around with the alternator wiring in order to install an isolator. It’s not necessary. Rather than add to the problem, I’d restore the alternator wiring to OEM specs, install the isolator correctly and replace the alternator with the correct version for your application.

You’ll get more responses if you do the legwork and post your schematics on a photo hosting site like photobucket and provide the links in your post here.


Thanks for your comments. I will work on posting drawings to a hosting site. I have them on png files, but maybe that will work.


Here is a link to the wiring drawings. There are other photos there, ignore them.


I don’t know your system so I can’t comment on the temporary setup but if you are charging to a battery voltage range of 13.5 to 14.8, that is OK; there should be no need to stop the charging within that voltage range. I and you probably too have no immediate way of knowing the accuracy of your voltmeter.


OK, much easier to understand. If you ask me, the isolator was wired correctly by the RV shop. The fact it worked properly before the road trip incident bears that out. Why not just buy the module with the regulator and return the wiring to the way it was? Far better than another band-aid on top of the mess you have now. Think about what will happen if you break down again far from home with this electrical spaghetti job. Will that mechanic be able to understand the mess? Probably not.


We had a similar problem with a '93 Caravan. To fix it, we ran an external voltage regulator. We clipped the green line, and ran a new line from the field coils to the external regulator. The blue line is a 12V battery source, and we tapped off it to hook it up to the voltage regulator.

The sad part is, we did this years ago. I cannot remember which terminal on the external regulator is for the green line, which one was for the blue 12V line, and which one was ignored (dummy). We used a picture from a parts catalog for a replacement connector to determine that.

But, the rest of the ECM was working fine. So we just did that, and it worked.


I appreciate your advice about buying a new computer and will probably do so. If my computer is OK otherwise, I might opt for the external regulator since computers seem to be a hard item to get, especially when away from home. I guess I could make the diagrams of all the spaghetti wiring, but I imagine a Dodge tech might look at them and just tell me that these aren’t Dodge diagrams and therefore do not count. That is what I was told at the dealer when I suggested he look at the diagrams in my Haynes book. He showed me a Dodge diagram on his computer screen and it was so simplified that I thought it was useless in the real world. It is what he went by though. Thanks for your advice, it makes a lot of good sense.


Thank all of you for your support and advice with my alternator/regulator problems, I really do appreciate it.

hambone, or BobTom, I can never remember who I am.