Dave;

Instrument "dimmer" lights are also not fused, coming directly from the light switch. Typically they don't work because the dimmer rheostat itself is intermittent or even totally open...try rotating the control back and forth when lights are on...if they flicker when doing this, it confirms the intermittent condition...in that case, I'd just bypass the control alltogether and make them light at full brightness whenever lights are ON.

Refer to wiring diagram again: http://www.intelab.com/swem/122S%20Wiring%20Diagram.jpg ...at (item 43) Light Switch...bypass variable control... disconnect three Red "instrument lighting" wires from their terminal, and connect directly to terminal 58b (two white wires). Voila!

Cheers