Baffling Charging System Question

[cosgig]

Howdy all. I have a longstanding charging system question that I vowed to get to the bottom of once and for all, and I need the help of the FABO electrical guru's to help me out!!! Heres the dilemma...

1966 Barracuda, 273, auto, stock wiring except for an upgrade to the Mopar Performance electronic ignition and later style voltage regulator and dual field alternator. Before I switched over the the dual field charging system I was running the original mechanical voltage regulator with the second field wire grounded to the case of the alternator and all was well with the charging system. Now that I've switched over to the newer style regulator I finished the second field wire to the ignition "RUN" side of the ballast resistor by splicing it into the blue wire coming off the regulator, as spelled out in an article in Mopar Muscle magazine. They chronicled the entire process and stated that when splicing in the second field wire and the newer style regulator plug to just make the splice for the second field wire to the blue wire at that location.

OK, now the problem... with both field wires hooked up, the guage reads slightly charging at idle, and during even slightly more than off idle will peg the meter. Here are my steps to diagnose so far...

Take off added field wire from alternator, original still hooked up= no charging

Take off original field wire, second still hooked up= still pegs the guage

Switch the field wires at the alternator= kills the car

Meter readings...

Original field wire hooked up or unhooked= no voltage

Second field wire unhooked= almost 14V at idle, climbs to high 14V then levels off at 2000rpm or so

Both field wires hooked up= second field wire voltage starts at near 14V and steadily climbs during exceleration to over 18V

Both wires unhooked and testing the field terminals on alternator= no voltage

I need to get this electrical system charging correctly but not overcharging, and I can't figure out why simply switching the field wires on the alternator kills the car and won't allow it to start. It seems like I have everything wired in correctly, and by the meter readings from the second field wire that the regulator is working, and the alternator is also working...so what gives???

I hope I spelled out all the necessary facts for at least some suggestions, and I'm hoping that someone in the FABO community will be able to solve this, and maybe explain the field situation, and maybe how the field thing actually works. I'm stumped!!! HELP!!!!

Thanks all for any input received, you all rock!!! Geof

 

[67Dart273]

Here's what's going on.

The old, original alternators had

ONE brush grounded

Second brush is insulated brought out to your green field connection to the regulator

So the regulator controlled field current through the field (brushes) to ground

=====================

The isolated field unit is only slightly different

It has both brushes insulated, both brought out to push on connections

The added wire is simply "ignition run" in other words it receives battery with the key in run

The original green wire back to the regulator NOW CONTROLS THE GROUND side of the field.
===========================


What is happening is one of several things. Either one brush insulator is broken, and one brush is shorting to ground OR

A rebuilder has installed one of their crappy "conversion" brush holders that converts the early (69/earlier) alternator to isolated field

and either that brush holder is shorting OR the dumb *** rebuilder LEFT THE ORIGINAL GROUNDED BRUSH in the alternator.

Last (almost forgot) the field itself could be shorted to the frame internally

You can confirm by checking continuity

A GOOD "isolated field" alternator will show continuity BETWEEN the two field connections but NO continuity to ground.

Inspect carefully to see if there is a third (grounded) brush

If you cannot find one, pull one brush out at a time and see if the continuity to ground disappears

Below is the old "round back" style and a picture of the original grounded brush. If this has been converted by a rebuilder, this brush may still be in place and must be removed:

Below is the newer "square back" style, ONLY made in "isolated field." If this unit has your problem either one brush holder is broken, or the field is internally shorted to ground

 

[daliant]

First thing to check is if your voltage regulator (Im assuming electronic) is grounded properly, loosen the bolts on the regulator and then tighten them a few times. Next (with the ign on) you should have 12v at one of the field wires and some resistance on the other, the electronic regulator controls the ground resistance in the field as opposed to the mech regulator which controls voltage to the field circuit.

 

[cosgig]

Wow, thats good stuff there guys. Daliant, I do have 12V at the second added field wire, and I'm assuming resistence at the other, but no voltage, so I'm assuming that the regulator is functioning properly and the ground to the firewall is good and clean.

That leads me to inspect the alternator according to 67Dart273's excellent post. This alternator is an "off the shelf" model, meaning I picked it up off the shelf at the shop and slapped it on when my good one went bad on me. I can totally expect foul play with this alternator, and will inspect it and check for continuity, and a few others I have for the correct dual isolated field model in which to use.

Thanks guys for your informative posts!!! Geof

 

[67gtx]

I don't know if you said the guage was volts or amps that your were looking at. If volts thats bad, if it was amps that's ok.

 

[67Dart273]

I don't know if you said the guage was volts or amps that your were looking at. If volts thats bad, if it was amps that's ok.

You might want to read the OP a little closer. What he described is NOT normal.

 

[cosgig]

Hey all, I am just updating this thread to conclude it for any who may have been following along. I did as 67Dart273 suggested and changed the alternator, suspecting a broken insulator around the field terminal. I am very relieved to report that the problem has been solved and that the alternator was indeed the problem. Thanks 67Dart273, you came through big time!!! Geof

 

[caferacerx]

excellent!

 

[67Dart273]

Did you find what the actual problem was? Glad you got it going.

 

[cosgig]

Hey 67, I believe it is in fact a broken isolator around the second field terminal, the one furthest from the output post of the alternator. I went through the entire system again, took off my regulator and made sure it was grounded, checked all my connections and wiring route and then changed the alternator to another one I had on the shelf that was working when pulled. It is about the roughest customer I've ever seen, but i didn't want to shell out the $60.00 for a new one until I was convinced that the problem was located. I am also leary now of rebuilt units off the shelf from regular parts stores because of the lack of quality to detail when rebuilding them, so I'm going to buy a rebuilt one from the Plum Crazy Garage, a company I have been using to core out starters and alternators. They are Mopar only, and although they only do date coded items, I will pay the extra $$$ to be sure my new one is rebuilt by a Mopar only expert, not some reman house that doesn't care!!! Thanks again 67Dart273 for helping solve this problem, it has been a pain in my side for way too long now!!! Geof