Gauge Lights Won't Come On - Help Please

[Gregski]

74 GMC half ton

headlights come on but gauge lights do not, I pull the headlight switch out twist it left and right and nothing, do it with both no key in ignition and with key in ignition in all sorts of positions, nothing

replaced all six bulbs

replaced all 9 fuses

tested light bulb under dash it is a good one (not related but would want that one to come on too)

removed headlight switch cleaned and rebuilt it (dont know how to test it)

dont know how to test with a multimeter or where to start, which wire is the power for those darn cluster lights?

advice needed