I have a 1966 Plymouth Fury III and I just went out and bought a new alternator and voltage regulator and it still wont charge(or at least when I pull the battery off while its running, it dies). Ive checked the wires and they are good. It could be several different things(or at least I think) I bought an alternator and it appears to have two different fields(the original only had one) and where the ground brush is(where it says GRD and there is a brush that I assume grounds itself to the alternator) there is nothing. So Im thinking its either the wrong alternator(which is funny because it has the right part number on it but if you go on advance autos website it P7001 looks like EXACTLY like what I need and not like what I got) or I got a bad voltage regulator, Which brings me to another question, To test if it is the voltqage regulator can I just cross the IGN wire(that goes into one side of the regulator) and the FLD wire(which plugs into the other side of the regulator) and pull the battery off and see if it still runs or will crossing them screw it up? The one pic labeled download(the stock photo) is the one I need, the pic labeled this one(the one I took with my camera and a flashlight) is what I got. Also The one I had/need has only fld and bat, so my car only has those two wires.

 

In my time, i have heard a lot of bad feed back towards the idea of pulling your + cable off of the post to check your charging system. This is not something i have tried though. When i am working with any type of electrical system i use a Multimeter. You can check the input and output of your VR and your ALT in seconds. you should be able to get a cheap one from Walmart or your local parts store. It does not have to be anything fancy, but some do come with settings to check your dwell and a tach. Might be something you want to look in to, more accurate readings for troubleshooting, and significantly safer.

 

Check ALL your ground connections and check for corrosion.

 

On a '66 Mopar, if the engine is running and you pull the + cable off of the battery, the engine will stay running IF your charging system is charging and die if the charging system is not charging.

It has been proven that a NEW voltage regulator doesn't mean it works, unfortunately.

If your alternator looks different than the alternator that you took off... you probably have the wrong alternator.

Back to the voltage regulator wires....
30 years ago, I had a regulator go bad, at night, and my battery was low on my first '68 Fury. I had about 30 miles to go to make it home, all freeway.
So, I bypassed the voltage regulator by just connecting the wires to each other and went for it. By the time I got home, due to the freeway speeds, I had blown out both headlights and cooked the battery because, the faster you go the more amperage the alternator is creating and the alternator gauge was pegged most of the ride.

Maybe for a quick test but, I wouldn't advise it!

 

First of all DO NOT EVER "test" a charging system by yanking off a battery cable. The newer cars get, the better the chances are you will damage some electronic device, including the ignition, radio, electronic regulator, clock, or anything else in the car that is "solid state"

Second, this "test" which you will NEVER find in any shop manual, textbook, or any automotive shop class, DOES NOT PROVE anything.

If for example, you had an alternator with one stator winding (they are three phase) open or shorted, or a couple of diodes open, WILL put out enough juice to run the ignition and "pass" this so called test.

Also, if you happen to have the idle speed set so low that the alternator has not "kicked in" and you remove the cable, the engine will die, even though the charging system is OK

So don't.

NEXT

Your "wrong" alternator can be easily made to function with your "old" style regulator.

The "grounded" field alternators ended in 69. From 70 and later, Ma used "isolated field" INCORRECTLY called "dual field" alternators

IT IS EASY to make a 70/ later alternator work correctly on a 69/ earlier car with an early regulator. ----Simply ground EITHER of the two field terminals with a short pigtail, and plug the regulator wire into the remaining field. Some alternators have a screw/ nut ground stud, others just use one of the frame bolts. Make up a short pigtail with a ring terminal on one end, and a "push on" terminal on the other. Makes no difference which connector you ground.

Aternatively, IF IF you can find the proper kind of brushes for a '69 alternator, you can pull the brushes out of the one you bought and install the 69 ones, one of which will fit the position marked "ground" in your photo. I have had trouble finding proper brushes. My alternator is out of a 77 Van, and NAPA took THREE TRIES before getting brushes which I had to "rob" two packages to get the "right ones." I am STILL AMAZED at this poor display

QUICK TEST

For a few quick tests of your charging system, simply buy a meter -- you need one anyway-- and with the engine warm, the battery "normalized" (ammeter centered after some running) and the engine at an RPM to simulate "low to medium cruise" then measure across the battery terminals. What you ideally want is more than 13.5, perfect is 13.8-14, or high end about 14.5. Higher or lower is cause for concern

If this is low, no charge, pull the field wire off at the alternator, and install a clip lead from the output stud on the alternator to the field terminal on the alternator. You should hear the alternator "grunt" and with the engine GENTLY brought up a little in RPM, the battery voltage should start to climb. Be careful not to ref the RPM too much, and monitor battery voltage. Do not rev enough to bring voltage over 15, 15.5.

If you get no output, check the voltage at the alternator stud. Should be close to battery. If you have battery voltage at the stud, but no charging voltage increase, you have something wrong in the alternator

If the voltage at the output stud is low, much lower than battery, you have a wiring problem in the charging/ output circuit, either the ammeter or the bulkhead connector is your no 1 suspects

If this test DOES show a marked voltage increase, you have either a wiring problem in the regulator/ field circuit or a bad regulator.

To check for that, unhook the wires from the regulator, and connect them with a clip lead, reconnect the field wire at the alternator. As above, the alternator should output "full tilt," and be careful of the RPM

If this test shows a charging increase, you need a regulator.

Most/ all? replacement 69 regulators, if you were to pull the cover off, are in reality now "solid state" insides. This would be OK if they were all good quality, but many are not. One recommended replacement is a Standard Motor Products no. VR-128 which looks different, but works fine.

PLEASE POST BACK because after you make some checks "there's more."

 

I grounded out one of the fields and it is charging now.

 

Yay!!

 

Al RIGHTY then.

Now make a couple other checks=====

check for voltage drop in the ground circuit of the regulator, as well as the ignition feed which is the "sensing" lead for the regulator.

First, if you have points ignition, make sure the points are closed. To do that, put one meter lead on the coil neg. terminal, the other to ground. Switch the key to "run" engine OFF

IF the points are closed you will read low voltage, if open you'll read "close to" same as battery. Bump the engine if necessary until the voltage goes low, showing they are closed.

Now stick one probe on the battery positive terminal, the other on the regulator IGN terminal. You are lookin for a very low reading, the lower the better, zero is perfect.

Anything OVER .2 (two TENTHS of a volt) is cause for some concern, 1/2 volt or more, call to action

You are checking the voltage drop in the circuit from battery -- fuse link -- bulkhead connector -- ammeter circuit -- ignition switch connector -- ignition switch -- back OUT the switch connector -- back OUT the bulkhead connector on the "DARK BLUE" ignition "run" wire -- and finally to the IGN terminal of the regulator

IF this drop is approaching 1/2 volt or more, it will cause overcharging. Check the condition of the bulkhead connector, the ignition switch connector, and the switch itself

NOW check the ground circuit. With the engine warmed up, running at high idle, and battery "normal," stick one probe on the battery neg. terminal, the other on the regulator mounting frame. Be sure to "stab" through any paint, chrome, rust.

Again, you want to see a low reading NOT over .2V. IF it is higher this indicates a ground problem between the battery/ block/ body

 

 

To 440roadrunner
First I’d like to thank you for this awesome information you posted. It’s been very helpful to me. Now after completing all your tests, I’m still unable to figure out the issue. My cars a 69 charger, it has a upgraded electronic mopar voltage regulator on the firewall and a two field power master alternator. Here’s what I have so far.
1. no charging with everything hooked up as it should be
2. did your test of disconnecting one field wire and putting clip leads from power stud on alternator to field post on alternator, result - alternator charging
3. did your test of unplugging the wires from the VR and jumping them together with both field wires connected. Checked both field wires for power and both showed 12.25v but alternator would not charge. Tried jumping from power stud to field wire with VR still disconnected and alternator would not charge. Plugged regulator wires back in with jumper still on power stud and field post and once again it was charging.
your explanation on this stopped at if the alternator is charging with the VR wires jumped together then the regulator is bad but it does say what to do if the alternator fails to charge on this test.
do I need to ground one field wire? Or does this still mean the VR is bad? Not sure why jumping the power stud to field stud works with the VR plugged in but it doesn’t work if VR is unplugged. I assume when the regulator is unplugged and jumpered together, the alternator won’t charge just like when I had it unplugged and not jumpered and tried to jump from power post to field post. But if regulator is plugged in when I jump from power post to field post the alternator charges so I’m assuming the regulator must be grounded when it’s plugged in and not grounded when unplugged and jumpered. I hope I explained this well enough to understand what I did so you can answer with what to do next.