Okay, well I decided to chase down my problem some more, and I FIXED IT !!!
you may recall, I and another poster were having issues with our 96 XLT's
SOME of the dash lights didn't work (Radio, 4x4, OD off, etc) when the headlights were on.
Also, the fluorescent displays ( Compass, Thermo, Radio, etc) didn't dim..
Well after chasing through the circuit, and testing the parking light relay, and dimming relay, I found the problem to be in the dimming module ( the rotary knob next to the headlamp switch)
I initially discounted this since the dash lights DID work, (and dim) properly, but after examining the wiring diags, I saw that there were 2 separate outputs, and one affected all of the above circuits I was having problems with.
After taking the front apron off of the dash (under the steering column, ) I rapped the module on the knob sharply with the handle of a screwdriver, and VOILA! it came back to life !
How long will it last ? who knows, but if and when it goes out again, I'll know what to replace.
Hope this may help out with some others that may be experincing similar probs.
Good Luck!