reason is that the indiglo's need a constant 12V to stay lit....then it uses its own dimmer which dims the AC current (not DC) running through. with the stock dimmer.....it decreasing the outgoing voltage.....from 12V max to 10 to 5 to 2 to whatever depending on how dim you want it. basically...the gauges need a constant 12V which the stock dimmer does not provide. check out my website (LINK BELOW).....this is the simplest way to do it....comes out clean and works efficient. read WHY i did what i did and you'll understand. g'luck