I not very good at explaining things but, I'll try. You really have to pull that dimmer switch to test it. Granted you could just unplug the connectors to it and test it in place but, a real pain. Hey it probably has to be cleaned anyway. Dome switch jiggling tells me that. O.K. get a cheap ohmmeter (harbor freight has them free with any purchase right now). The dimmer is a variable wire wound resistor with a switch. When the dimmer is rotated to the (click) switch position, the middle contact should show a short between both the other contacts (or very low resistance 1 to 2 ohms). When un-clicked, the middle contact should show a open between it and one of the outside contacts but, it should show a short between it and the other contact. Leave the ohmmeter connected between the middle contact and the one showing the short and rotate the knob. The resistance should start to increase (which would dim the panel lights). I'm guessing that you will not see a short between these two contacts or a resistance change. That means that the wire wound resistor is really dirty or it has opened up. Granted this is assuming that your connections are all sound to the switch and fuse box. Let alone the instrument panel. (round plug on the back and maybe a bad circuit trace, also grounds). If you see the resistance jumping around between middle and the one that should change, take Roadcuda's advice and clean it good. Radio shack now sells DeoxIT. Great stuff but, pricey Catalog #: 64-249. Yes you could jumper from middle to top (dome light) then middle to bottom (panel lights) (with the headlights turned on) for a test but, I don't like the jiggling to light the dome. Switch is dirty. You could also leave it plugged in and short middle to bottom (tan to yellow/with tracer) and light your panel lights at full brightness and live with the dirty dome switch. Once again this is assuming everything else is sound. Sorry this is so long, just trying to help and I can't sleep.