Alternator / Strange Extra Wire?

[LordFly]

So I replaced my alternator last night with a proper one from DMCMW. The plug on the new alternator has a single wire coming out of it, the only one had 2.... One of them went into the factory harness (which is where I put the single wire from the new one), but the other was routed up through the engine bay and attached to a white wire on the yellow plug (see blue crimp on connector in picture). Anyone know what that would have been for?

I had replaced ALL my dash bulbs with LEDs, and with the old alternator, the battery one wouldn't shut off unless you reved it to about 3000rpm, then you were fine for the rest of your drive. The the new alternator and single wire, it would not turn off, which I believe it more proper. I threw a standard bulb in the battery one and now it seems to work the way it's supposed to. So that extra wire was doing something in regards to that.

20178

[Ron]

The wire in the yellow bulkhead connector has 12V when you have the key on. It goes to the ignition ballast resistor. There is not enough info the say for sure, but they probably tapped it with the blue wire trying to use as an exciter for the voltage regulator...revving the engine, with some regulators, will make the alternator kick. This usually means there is no power on the "other" wire (Brown/Yellow)...that is what happens when you put a LED in the battery light socket....