I assume the light is hooked to the #1 terminal? I also assume #1 is what you are calling the "excite terminal."
The colors of your wires don't help. When you are facing the alternator from the back - the two spade connectors on top are #1 (excite) to the left and #2 (sensing wire) on right.
If I read you correctly, you say your light goes on when hooked to #1 but no charge. You then jump 12 volts positive to #1 and it charges? If so, obviously you're not getting enough power through the light wire to excite.
Since it charges when you jump, RPM cannot be the issue. But do keep in mind that the 10SI or 12SI needs to spin 1600 RPM to charge. If the engine idles at 800 RPM, the pulley ratio must be at least 2 to 1.
Same-Day Shipping! Most of our stocked parts ship the same day you order (M-F). Expedited shipping available, just call! Most prices for parts and manuals are below our competitors. Compare our super low shipping rates! We have the parts you need to repair your tractor. We are a Company you can trust and have generous return policies! Shop Online Today or call our friendly sales staff toll free (800) 853-2651. [ More Info ]
TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.