If the other lights do the same dimming I am thinking the regulator is wearing down.
If the other lights stay normal I’m guessing a bad or loose connection.
There once was a biker named Double-Fat. Who rode all over like a cafeined gnat.
When he once tried some Frenchy booze, His skills improved the more he wooz'd-
And he was heard to mumble, "Dood- that's where it's AT!"Uncle Ernie-4-24-2011