I bought an altternator...which has two 'fields' and the 'bat' post on the back. One of the fields goes to 'low output 12 volt...at the ballast resistor'...thru the volt regulator. The other...according to the wiring...goes direct to the [same] ballast resistor. Finally, I got the alternator to start to show somw output...but it is still in the 'discharge' mode on the amp meter.
Question...should one of these two 'field' terminals...be a ground?? Do both 'field' terminals...'supposed to' originate from the low volt side of the ballast resistor...one going thru the volt regulator? Should one of the 'field' terminals...be grounded? It is very confusing to me....and every thing else in my recent conversion works....except for getting thios alternator to charge.
Anybody have any idea to help a poor me out??

Thanks!!!

We would need to know the year, make and model of the car.
Both dual and single field alturnators were used over the years.
DD

The engine came from a 77 van. The vehicle itis going into is a truck...that has a 77 truck wiring harness, but the harness also had at one time...a 100 amp alternator.
I am thinking that (probably) one should be a ground...does this sound possible?
I can switch 'field' wires around....with NO change. I can even unplug the volt regulator..and no change. Got me confused.
I just do not know. The alternator, I bought for (application) of 77 or so van...slant six.
The harness that went in the compartment...was that of truck..with 100 amp alternator.
It's beyond me.
Sure appreciate any/all help.
JWW

You should have three wires attached to your alternator. The large gauge wire under the screw terminal goes to the battery. The other two should have spade connectors to the field windings in the alternator.
One of these two should be connected to switched 12 volts (12 volts ONLY when the key is on). On the diagram below this wire is blue with white tracer. The green wire goes to the voltage regulator.

Hope this helps.

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Rafa

Hecho en México

THANKS !!

I have had the thing wired almost similarily...except I have the 'resisted' side of the ballast...as feed for the alternator....not the full 12 volt side.
I will re-do this tomorrow. I again, appreciate your help.
I did, at least...get some 12 volt action...from the pos output...something not before occuring.
JWW

Please notice....BOTH field wires run to the voltage regulator, the switched wire (blue) is just T'd off instead of going straight to the regulator(it makes several other T's as well). That diagram is nearly identical to my '87 for the charging system, minus the ballast resistor.

-S/6

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The "Silver Bullet"
87 Ram D150