My '98 +4 instrument lights vary from nil to bright in roughly the top 1/8th of the 'rheostat' travel.
Cheers,
While hunting under the steering wheel column, just now, I found my Rheostat Knob on the RHS near the door. (only took 10 months to notice)so will have a play with that if we ever go out in the Dark (whooooooo)
There is another very tiny narrow protrusion/button/twiddler under the dash roughly under the speedo?
Not sure if it is for turning or pushing so have left well alone at the moment. The speedo does not have a trip line so I imagine it cant be for re setting that?
Any Ideas what its for? Makes me sound stupid, but I cant find any reference to it.

I don't think we have an Ejector Seat!