weird charging system issues.

Hey guys 

              I have a 1970 rebel machine I recently got up and running. It has a new harness new vr and rebuilt alt.

                After I put everything together it worked fine for 600 miles or so of shake down miles. upon start up meterd the bat wile running to verify charging system works. Then just recently On a drive the car would not start due to weak batt slow turn over.
 Trouble shot charging system not working. jumperd orange wire  to green wire on alt/VR (on alt side) plug wile car running Meter said alt not charging. Sourced rebuilt alt installed hooked up still not charging. disconnected alt/ VR plug and again jumperd the orange and green wires still no charge.
meterd for voltage the orange wire read 12 volts.  jumperd orange wire to green meterd voltage reads 2.5 (motor running). began to scratch head WTF jumperd the yellow wire to the green alt began charging right now.

                      The ALT light in the gauge panel comes on with key and stays on when running. the old alt was a 35 amp model and the new one is a 55 amp both are motorola's.  both have the green wire hooked up to the feild terminal spade and the ground is on the plate next to the field . the orange wire is on the post next to the isolation diode (not on it but on the AUX terminal).  and the power is on the big post on the isolation diode. this is the way the tsm shows it. the 35 amp alt had the orange wire hooked up on the isolation diode beside the big post for the big red wire.

                    now where does the orange w/black wire get its power from? guessing this may be my issue.
                     Chris


Edited by iapexl8r - Sep/26/2015 at 3:35pm

 The alternator that you show in the pic appears to be just like mine (the 55amp) but my tag is yellow.
today I went ahead and hooked it up just like the 35 amp model with the only change being the orange wire moved from the aux terminal to the isolation diode smaller terminal. and guess what it works. the light goes out and the bat voltage goes up to 13 vdc at idle. I wonder if I have the wrong regulator or alternator. will post pics.    
                                                                      chris

There will be a resistance wire, unless The Machine is different from every other 67+ AMC.

The regulator can only be wrong if the connector is wrong. The regulators for 71 and later, the years AMC used alternators with NO isolation diode, uses a different connector - they flipped the male and female ends to ensure they regulators could not be interchanged.

Yellow tag? What is the model number on the tag? 1970 and prior would be black or teal (sort of a turquoise).
1970 55 amp would be 8AL2009K (the K indicates 55 amp in certain years).
If the car was EXTREMELY early build and I mean VERY early, it could be A12NAM605 but because AMC was using stock from before about May 1969, it would be an early build car to have that model as in spring of 69 Motorola announced that as of that time they would no longer make alternators with customer model numbers, they would all be standard Motorola model numbering from about May 1969, so to use a A12NAM on a 1970 model year car it needs to be an early one.
Otherwise 1970 and later used 8AL, and 1971 was the switch to NO isolation diode - from 1971 on they used Motorola alternator models with the internal field diode, more like Delco and others were using.
So to prevent mixing of regulators, a change was made to the connector, 69 and 70 used
regulators with MALE connectors while the harness has female, and in 71 the regulator used FEMALE flat spades while the harness has male connectors.

(from this page - http://theamcforum.com/forum/alternator-and-regulator-id-and-connectors_topic13346.html)

Now, ya wanna know something I find interesting? You changed the location of the orange wire, right? Well, no, you didn't. Not really. Why? Because both of those studs are exactly the same electrically! They BOTH go directly to the heat sink of the positive diode array in the alternator.
They only used the upper one closer to the brush or field connection for convenience.
Both of those are carriage bolts pressed into the positive diode and staked in place, they run through the rear frame and are insulated from the rear frame using nylon sleeves or tubes. The nylon insulators push through the two holes on the "left", and the bolts or studs for the positive diode slip through those nylon insulating tubes, then there's an insulating washer that goes over, then the nuts, etc.
So electrically they are exactly the same, they have to be, it's impossible for them to be different.

This is the proper 1970 35 amp. The isolation diode sits over BOTH positive diode studs, and the take the aux/reg connection from the "top" one. Convenience.
For the 55 amp, the isolation diode is a double diode in the head sink, is longer, so they mounted it differently. But the one stud is STILL directly connected to the isolation diode, but the one on the "right" is insulated from the NEGATIVE diode array stud by a thin nylon sleeve and two insulating washers.
So the 55 amp isolation diode connects to one positive stud, and is anchored by a negative diode stud but is insulated from it, the 55 amp isolation diode connects to both positive diode studs and is not insulated from either - because they are identical in every way except WHERE they are. Not in what, but where.

Note on the 35 amp the isolation diode is directly connected physically and electrically to both positive diode stud.


Note in this photo the bottom of the picture you can see the insulating washer between the longer 55 amp isolation diode and the negative diode stud, the upper part shows the keps nut directly on the stud and isolation diode.




In this picture the two studs closest to you are - on the right the negative diode stud and on the left the positive diode stud. Note on the right stud a washer and a nylon sleeve - this is to insulate and isolate the longer 55 amp isolation diode from the negative stud. They want it anchored physically but NOT connected electrically, while the stud on the left is positive output so it does need to be physically and electrically connected to the isolation diode.



Again - note the insulator on the right, but on the left the nut cuts directly to the isolation diode.




OK, these are the two studs that come up from the positive diodes inside. They are identical, they are both pressed into the diode heat sink, both insulated from the case or frame (note the fiber washers) and the one on the left is what you normally connect to for the reg/aux orange wire - the one on the right is what you moved it to - ah, but they are the same. Those two studs form the legs of sort of a "U" so one leg is simply the left leg of the same U while the other is the right leg of that U.



Here's another view - both of these studs put out exactly the same thing - except one has a connector for the orange wire while the other is connected to the 55 amp isolation diode.



On the 35 amp because the diode mounts over BOTH positive studs, they provide a place to connect the orange wire -



So the only difference really between the 35 and 55 is how they mount the larger isolation diode for the 55 - all other wiring would be the same electrically.

The rear frame has two holes that are larger - at the top in this picture - for the nylon insulating sleeves, the lower holes in this photo are for the negative diode studs, they connect to the alternator frame so are not insulated.



And finally, I'm now confused because you basically moved the orange wire from the stud on the right to the stud on the left - both protrude from the frame or case through nylon insulating sleeves. Note the differences? Yeah, there aren't any.......



I am always nervous with remanufactured electric, carburetors and brake parts.........
Unless the wiring harness is wrong for a 1970, I can't see how the regulator could be wrong unless they really messed up - wrong part in the box, etc.
One would over-charge and the other would undercharge due to the 1 volt drop across the isolation diode.
A 1971 regulator on a 1970 alternator would under-charge, a 1970 and earlier regulator on a later alternator with no isolation diode would over-charge.

How about something as simple as the body ground?  I was getting no charging on my alt gage in my 1971 Javelin AMX when we started it up the first time.  My buddy said to check the ground from the engine block to the engine crossmember.  I had powder coated the front cross member so the eyelet was not grounding.  We did the same with the starter, but that was obvious when the starter would not turn over.

71 Javelin AMX O.O. wrote: How about something as simple as the body ground?  I was getting no charging on my alt gage in my 1971 Javelin AMX when we started it up the first time.  My buddy said to check the ground from the engine block to the engine crossmember.  I had powder coated the front cross member so the eyelet was not grounding.  We did the same with the starter, but that was obvious when the starter would not turn over.   Might be as simple as that?   Steve

That can definitely affect or impact accessories, etc. as they often ground through the body of the car in some way. As an isolated system in itself, if the battery - goes to the block and the regulator is properly grounded to the alternator through the black wire from regulator to alternator, it would still function, but the rest of the car wouldn't necessarily realize it!
If battery neg goes to the block, the alternator is bolted to the block and is thus grounded to the block and through the block to the battery, and the regulator is properly connected to the alternator through the black ground lead, it would charge and should charge properly as far as keeping the battery up - but the accessories would struggle.
The alternator and regulator connect directly to each other and to the battery so you could lift the engine out of the car, unscrew the regulator from the inner fender and hang it on the engine stand by string and as long as the battery was still cabled to the block and the alternator was still connected output to battery POS via the starter solenoid battery-side terminal, it would work fine.
But a volt meter connected to ground through the chassis would read low voltage due to the voltage drop caused by the poor or lacking engine to chassis, and thus engine to meter, ground.

The biggest problem is with accessories or items that draw appreciable current because smaller things can ground to the engine though throttle cable, drive shaft, etc. -poor but works for low draw items, while bigger things, such as the starter, etc. will typically fail.
The volt mater may work but may read low because of the lack of meter ground to block.

My own 73 Javelin has brighter headlights now since I put a cable between where the battery NEG bolts to the engine block and the chassis at the crossmember. The bolt was in the cross-member but there was nothing connected to it! I thought why the heck would anyone put a bolt, washer and nut in that hole - with it holding nothing, no cable, nuttin'. Silly, then why bother putting the crazy bolt back in?
Due to the headers and extreme heat in that area I used a long heavy cable from the front end of the block where the battery negative bolted, up and then down to the chassis avoiding the headers. I still smelled hot wire insulation after a short drive with it. But it seems ok, and the headlights are brighter now, too.

I think it was grounding via the throttle cable as when I put the NOS alternator and NOS regulator on the car I noted the throttle was far harder to push than it was before. The PO put the cable down too far so it's hard to push the throttle the first little bit then it get very easy and you take off like a shot, but after the new alternator and regulator I almost had to stand on the throttle to get it to respond. I suspect it was getting the throttle cable hot with the load and sort of messed it up.
Man does that thing crank very nicely now and the beast starts like never before.
Amazing what good a decent ground does for lighting, ignition systems/spark and so on! LOL