By the way....
The way that light works is by a developed "difference of potential". One side is always at 12V thanks to the battery, the other side is connected to the output of the alternator, and it will also be at 12V if the alternator is generating enough voltage. Since both sides are at 12V, then there is no difference of potential - hence no current flow through the light.
If the engine is running below a certain idle, then the alternator is not producing enough voltage, so a difference of potential develops and current starts to flow through the light.
The difference of potential is inversely proportional to the voltage being generated which is why the light is brightest when the engine is off. It comes on slowly as the engine speed slows down, first dim, then brighter and brighter as the engine slows more and more.
Citing all of this electricity mumbo-jumbo, it appears to me that the side of the bulb that is supposed to be hooked to the alternator is actually grounded out somewhere.
I hope this helps
On their death bed, nobody ever said, "Gee I wish I'd spent more time at work!"
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