03 GMC 2500HD Dash Light Problem

[gmchd2500]

Backlight for gauge cluster, headlight, fog light and temperature controls out. dimmer still operates odometer, radio and dome lights correctly...

i find it hard to believe that every light burned out in the circuit at the same time. anyone have any suggestions or knowledge on how to test maybe individual circuits ...or where to get schematics for this circuit. the gauge cluster has been recently comppletely overhauled new bulbs/stepper motors so i feel like it must be something in the common for the negative side ... but i'm really open to any suggestions before i tear anything else apart.

Also, tested voltage output from dimmer switch ... also correct.

[2001HD6.0]

there is a fuse I forget what its called that controls all that.

[gmchd2500]

It's good checked that

[scottod17]

I hvae the 02 denali,same thing but now the dimmer just stopped working to,it is either full or off,with no lights to iluminate the controls.if you find out what it is please advise