2 Field Alternator Question

I have spent quite a bit of time going through all the threads I can find on changing out the old single field alternator to one with the 2 field connections but can't seem to find the info I was hoping to find. I am changing out my single field on my 69 Dart due to an unfortunate battle with fire, I have read that you can just ground the one field and leave the other wired as normal, seems simple enough, in my reading I found some info that upgrading the VR would create a more stable charging system, update to wiring is simple enough, maybe I missed some info?

My questions:
is there anything actually gained by updating the VR instead of just grounding the extra field?

I am swapping out the old distributer with a ready to run type similar to a MSD/Mallory, it seems like this could cause an issue with the updated VR with the wiring, anyone done the change where they had to tie both ignition wires together that connect the ballast resister for a different distributer? maybe overthinking this one.

Ok, on the two post field alt.....yes, ground one, and it will work fine, I did upgrade the vr with a circuit board type from auto zone, just a better product than the old points style, have not had any problems with this setup, been running it for years.

On the dist.....a lot of after market drop in dist. allow you to eliminate the ballast, check with the manufacturer for installation, but you would connect the two together to bypass....no problems whatsoever with the vr.
higgs

Thanks HH, the 2 ignition wires will be tied together, I will use a really to switch a direct battery 12v to make sure no weak voltage to the new coil and distributer. Do you know if that would affect the updated VR when part of what is does is complete the ground? Part of reason asking is availability, seems the new style is readily available, old style I will need to keep a back up it seems, overall doesn't really sound like a new VR would provide any better stability with a good install and good wiring.

Just FYI... there aren't 2 fields. Every alternator has a single field with a positive wire and a ground wire. I must back up a bit and say welllll not exactly. The early design had a positive wire only. The field was chassis grounded just like most everything else on the car, so no actual ground wire. That voltage regulator modulated the positive side of the field. This is called closed field.
The later design is called isolated field. The regulator modulates the ground side of the field via the actual ground wire.
I suppose someone here could explain the advantages/disadvantages of both designs and why factory engineers made this change. When I changed from 36 amp round back to 60 amp square back alternator I figured I didn't need to be so enlightened. I could just follow the lead of the factory engineers and add approx' 8 feet of blue wire to my harness.

This is the modification I did to my '69 Dart. I was getting flickering on the lights and varying voltage. This cued my problem and allowed me to run a adjustable regulator (I set it to 14.5 volts while driving). I also added a 10 gauge wire from the relay battery stud to the alternator battery stud. This takes most of the load off of the bulkhead connectors battery terminal and also the alternator gauge. Doing this however will keep your alternator gauge from reading correctly so you'll have to put in a voltage gauge to monitor charging. I actually put all of the wires on the back of the alternator gauge on one stud so mine doesn't read anything.

Thanks for the reply's all, goal now is to get it back operating this weekend, will just ground the extra field to start with.

2 field alternator, gutted ballast and spiced the wires thru it, just to appear stock and made it easier, grounded one field to case, ran a ground wire from there on the alternator to the vr to the battery.

Electronic VR part # 35-300 on ebay, looks identical to stock and connects the same way.

Wouldn't keep a charge until I replaced the stock vr.

Bypassed ammeter, added volt gauge, msd, etc.

billsdartgt said:

Thanks for the reply's all, goal now is to get it back operating this weekend, will just ground the extra field to start with.

Click to expand...

I don't have an answer as to why they decided to use a ground controlling regulator in '70.
You certainly can use the feed controlling regulator as you plan.
Just be sure to charge the car battery on a charger. That will reduce the electric load on the new alternator, the old RV, and be better for everything.
Especially because many rebuilt/repaired alternators, especially squarebacks, have a higher 'rating', and may draw more field current under high demand.
A discharged batttery is one of the highest electric demands placed on stock system.
Charging Battery with Alternator - Warning