4020 12v Conversion - Gen Light Not Working

I have a 1966 4020 diesel which has been previously converted to 12v including starter. Alternator is a 12v 3-wire. Everything works except dash light. Charge (Gen) light does not work (i.e. does not come on with key and off when started). Light will turn on if manually grounded but then does not go off. Don't think it is wired correctly with alternator. How should this light be wired correctly using a 3-wire alternator? Appreciate any help....I hate wiring!!
 
Short version is:

One "side" of "idiot light" gets powered up when key switch is "ON".

The other "side" of the light/lamp needs to be connected to the #1 terminal on the Delco 12 Volt 3-wire alternator.
 
Should be a black wire that used go between the generator voltage regulator to dash board. This should be the idiot light and should turn it on when grounded when key is on. As Bob states, it is supposed to go to #1 terminal on the alternator. Which begs the question what is connected to #1 terminal on the alternator right now? That mystery wire may have to be removed in order to get the light working as it should even when hooked up to #1. I suspect the mystery wire is added on and would parallel the idiot light wire and thus defeat the function of idiot light when both wires are connected to terminal #1.
 
If it ISSSSSSSSS charging ????? I'm like as posted below, my best guess not being there is the Alternators small side 1R terminal is receiving excitation voltage from somewhere but NOT via the idiot charge indicator lamp. If you remove whatever is now on the 1R side terminal (keep it protected from shorting) and wire instead from the idiot lights downstream terminal (NOT where it gets voltage when key is on) I bet Bob and Lee are correct LET US ALL KNOW !!!!!!!

John T
 
just unhook the wire with the diode in it, from where it is hooked now, and hook it up the the wire coming from the light.
 
David, He may not have a "diode" since this is a Diesel ??? But no tellin how it was rigged up lol

John T
 








The original 24 volt switch has a 50 ohm resistor built into it. Since the generator light circuit is 24 VOLT the resistor is necessary to protect the 12 volt generator light. Some of the later 24 volt tractors have the resistor in the wiring harness for the generator light. An ohmmeter will tell what you have. With a 12 rather than a 24 volt supply, you don't want this resistor.







the
 
Hey no problem, Thanks for the shout back. I forgot myself for a while it was a darn diesel as were so used to thinking of a gas tractor that needs a diode or resistor......

John T
 

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