The idiot light does the following: When the key is turned on but the engine is not started, the, regulator (inside the alt) acts like a ground (electronically) The voltage from the key ACC terminal should be 12v to the idiot light, and because the alt regulator #1 terminal is in ground state, the light should show bright. When the alternator starts, the 12v that passes through the light is detected by the regulator, and the field is turned on. Now it should be charging. The regulator detects the charging (from the #2 terminal voltage) and applies charging voltage to the formerly grounded #1 terminal. Now the idiot light bulb has 12v going to both leads and it has no flow through and it goes out. Your tractor has a glowing idiot light when running, thus the balance between the charging voltage, and the supplied voltage at the ACC terminal are not the same. This is often caused by a poor connection in the voltage going to the Key, or a bad Key contact on the ACC terminal, or it could be from Alt brushes going bad, or a bad regulator. We really need real voltage readings to get to the correct answer. But I will say that if you bypass the key and light (as you did) and it charges, I would put the blame on the idiot light circuit. Because you have a idiot light, try this. Use a jumper with insulation to avoid shorts, and connect 12v directly to the switch side of the idiot light. If joy, try hooking the wire now on ACC to the terminal connecting to the coil. THis should work because the idiot light prevents the engine from continuing to run (it cannot pass enough current. A volt meter with a needle style readout (not digital) is far better to check this system, (really needed) Jim
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