Here's a twist for you....it's on my tractor.
John Deere 2640 I use for light bush-hogging and stump pulling on the farm. Noticed the batt was dead and when running I put my voltmeter to the alt it showed the same voltage as the batter (after I recharged the battery of course).
Alternator on there was the same Delco Remy as the one on my Jeep, and apparently was added later as there are wires going everywhere up in the alt area.
SO, what I have now is the wire going to batt, and the plug with two wires coming off. I know from this post
'#1' or 'Excite' on the left, '#2', 'Sense' or 'Sample' on the Right, 'BATT' terminal on the back...
'#1' or 'Excite' will need a resistor or Diode to work properly.
Many times, the resistance from an 'Idiot' light bulb will be enough.
Vehicles without an 'Idiot' light will use a Resistor Wire like you have in the picture, (Small, Brown, 10 to 15 Ohms),
Looks like on the tractor the excite wire is just hanging there, so I'm guessing that could be the problem (not sure if it got torn off or what).
SO, to test this alt, it SHOULD be as easy as putting #2 "sample to the batt terminal, but do I just add a resister wire and hook it to the batt terminal too?
I know it's not a Jeep, but wondering how I can hook it up to test it and see if the alts bad or if I have a wiring issue.