Instrument cluster dead

[Cathe Conroy Kennedy]

I have an 04 Silverado, 1/2 ton, extended cab, 5.3L.

The instrument cluster stopped working 7/2018. We sent it out to be rebuilt. Worked fine until a few weeks ago. Now it will work erratically or not at all. I bought a cluster at the junkyard and that cluster worked fine on the truck that it was taken off of but will not work in mine.  

We took a multimeter to the wires on the back of the cluster panel and the orange wire was reading 3.5-5. We also checked the ground straps and they were still connected to the truck.  

Does anyone know where that orange wire starts at or knows where the instrument voltage regulator is located?