I am trying to troubleshoot a problem on my "02" 2500HD. The bright lights won't come on. I have the following voltages: Purple wire - 12.05 on bright/11.95 on dim; Orange wire - 12.09 on bright/12.02 on dim. I have tried new bulbs (which didn't help). I got to thinking that I really shouldn't have voltage present on both wires. I am working off of a Haynes manual wiring schematic. I am starting to think that my dimmer switch has failed, but really want to get validation/ideas before I spend the time and money replacing the multi-function switch.... Your assistance would be greatly appreciated!

 

Orange wires are your 12 volt supply. Purple is the ground when high beam is selected. Open when low beams are on. Low beam ground is yellow wires. Shares the same ground as high beams just toggles in the dimmer switch as to which one is being used. Seen mice build nests under the underhood fuse panel and chew the wires. Just something else to check.