You have a later-model generator/regulator system than the vehicle had when it was manufactured, and it appears to be wired incorrectly. There should be two wires attached to the left side of the regulator as it shows up in the picture, armature and field, which will go to the generator. The third wire will be routed from the regulator to one side of the ammeter on the dash and from there to the battery cable terminal at the starter. You have an early version of the 3-unit regulator with three sets of coils under the cover, a cutout relay behind the battery terminal, a current regulator behind the Arm terminal, and a voltage regulator behind the Fld terminal. If you can get a model number from the regulator, I might be able to provide some adjustment specifications for it.
Jerry

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