Regulator 6 Volt

I'm adding a 6 V pos ground regulator to my AC B. It has three terminals (L) Lights, BAT, (F) Field, I understand those but there is an unmarked terminal underneath, what is that for?

I would guess it had a cut-on the generator like early letter series Farmalls. I am not sure that you can use a regulator on what is probably a 3-brush generator. But then what do I know--electricity is all just magic to me.

On many 4 terminal VR's (BAT FLD LOAD ARM) the terminal underneath or off on one corner by itself or not labeled is GEN/ARM

GEN/ARM wires to gennys ARM post
FLD wires to gennys FLD post
BAT wires to load (NOT battery) side of Ammeter (if it has an ammeter otherwise to hot ungrounded battery post or feed source like maybe
on a starter switch input where big battery cables attaches)
LOAD/LIGHTS feeds hot battery voltage to loads like lights or ignition often to the BAT Input terminal on those switches

4 wire VR's (BAT FLD LOAD ARM) can used or 3 terminal VR's (BAT FLD ARM) can be used and they can be interchanged if wired properly

On a 3 terminal with no LOAD terminal loads wire instead to the Load (NOT battery) side of ammeter

SUMMARY the one underneath or by itself is the GEN/ARM and it wires to the gennys ARM post

If I missed anything the other fine gents can add to this

John T

1) If the tractor originally had only a 3 terminal VR (BAT FLD ARM) you can still use the 4 terminal if wired correct, see above HOWEVER I have no idea if the VR will match and work properly properly with your genny.

2) If the tractor originally had ONLY a 2 wire Cutout Relay (BAT and ARM) its possible to convert to a full fledged Voltage regulator which has a Cutout Relay inside it HOWEVER the genny may or may not mate up properly with a Voltage Regulator. If it had that original and I was converting to a full fledged VR I would convert the genny to a 2 brush if its a 3 brush now.

3) The VR will be different if your genny is a 2 or a 3 brush even though its possible to make a crude conversion and it still works even if not engineering correct or perfect, Ive see it done

4) I have a suspicion the new VR may NOT be a match or original for that tractor ESPECIALLY if its a 3 brush and used a manual Low High light switch charge control system although it can still be converted (to a VR) if wired properly

5)Are you sure the tractor used a 4 terminal VR instead of a 3 terminal ???

6) Some older units that only had a 2 wire cutout relay used the Light switch for Low High charge control in which case the gennys FLD post wired up to the light switch. If that system is converted to a VR the gennys FLD wires instead to the VR's FLD terminal NOT the light switch

John T

Yes just get the regulator made for your generator

(quoted from post at 19:23:39 08/15/20) I'm adding a 6 V pos ground regulator to my AC B. It has three terminals (L) Lights, BAT, (F) Field, I understand those but there is an unmarked terminal underneath, what is that for?

Click to expand...

Are you adding, or replacing?

The tractor did not have a regulator, I'm trying to modernize it. Thanks for comments.

If modernizing from a cutout relay to a full fledged VR it wires as I posted below, but Id consider converting genny to a 2 if its now a 3 brush. It can still work as a 3 but that VR was likely not designed for an older 3 brush, I cant know from here. Even if not perfect however, if wired as below it can "work"

John T