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Faunsdale, AL | Yes
Need to unplug it. Most internal regulated alternators are intended for the excite wire to be keyed power. Usually you’ll find it is warm when everything else has cooled down and you may be able to detect that the rotor is still magnetized. On a Delco, you can stick anything steel to the rear bearing area and feel it pull in. That’s not as noticeable on others.
The one wire regulator used in the Delco 21 and 22SI large frame alternators has an internal strap connecting the output stud to the #1 regulator terminal where the excite wire connects. Those regulators are designed to not kill the battery though.
If the alternator is good, you should be able to give it a flash for a second after you start the engine and it will build up voltage and stay excited until you shut it down. I have installed a short wire on the output stud that will reach the excite terminal but not really touch anything else. Just clipped the wire off so it would be hard for it to short to ground, but I could purposely touch it to the excite terminal after starting a pump or something like that. It was part of the starting routine.
When you see the voltage jumping around a little, I expect you’re dealing with bad brushes or some other bad connection inside. If it momentarily looses the field connection (that’s what the brushes do) it will need to be reexcited. With the wire from the harness in place or your jumper, that source is always there and the thing picks back up and charges again until the bushes or whatever finally fails completely.
Edited by ccjersey 12/11/2025 20:34
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Alternator exciter wire on Gleaner A75
