idiot light stays on

[rkoronka]

I have a 2510 jd tractor and the idiot light stays on. The belt is tight and the alt. shop checked the alt and said it was fine. The wires are hooked up top wire on clip is on the key switch when key is hot. the bottom wire and the wire on back of alt are tide together and go to the starter bolt on the silnoid.Help on this would be many thanks.

 

[rustyfarmall]

An alternator has got to have 12 volts to it to "excite" the fields before it can generate any electricity. Somewhere in your wiring harness is a loose or dirty connection, or a broken wire.

 

[Anonymous-0]

Sounds like you have a 10 SI Delco alternator fitted to your tractor and all wiring is correct.
Check that you do have Battery voltage to the big BAT terminal on the alternator rear and to the #2 regulator plug terminal, the one that also goes to the big BAT stud.
The gen light uses the #1 regulator terminal on the alternator as a ground to make the light come on and supplys voltage to "excite" the alternator at the same time to get it charging.
Some alternator regulators that are a little off spec will excite and charge on an alternator test machine that supplys more current to the #1 alternator regulator terminal, while this same regulator will not work with the tiny fraction of an amp supplied by your little "idiot light bulb.
As a test, carefully touch a jumper wire from the big BAT stud to the #1 terminal in the top of the regulator plug with the tractor engine running at 2/3 speed. You only need to do this for a moment,then see if the idiot light goes and stays out. If this makes the alternator charge and the idiot light goes out, You need a new regulator that is a bit more sensitive, or you need a higher wattage bulb in the idiot light, or add another idiot light wired in parallel with the original to feed more "excite" power to the alternator. This "hidden" idiot light can just be taped to the harness under the cowl.
GM cars had the one visible and one hidden idiot light as standard equipment for years. It about drove many mechanics crazy,trying to find out why the alternator was slow or unable to excite until they realized that the visible light was working, but the "hidden" one was burned out.