Toyota Repair: Loss of Dash Lights, ash tray, dash lights

Question
Ted,
I have a 1998 4runner.  Recently I lost my dash lights, HVAC lights, gear position light(on the floor) and ash tray lighting.  I have turned the dimmer knob all the way in both directions with no result.  All the warning lights still work.  checked fuse under the dash marked gauges as well as under the hood, marked tail.  Took panel apart and checked all the bulbs.  At this point I'm thinking the rheostat is bad.  How would I test it before buying a new part?
Thanks
Nathan

Answer
The rheostat has a green wire going to it. This should have battery voltage with the headlight switch on, the white /black wire is ground , connecting a testlight to the gree/white wire and ground should increase/ decrease the testlights brightness.
Using an ohm meter the resistance between the white/black wire and the green wire should change when moving the rheostat.