In Virginia, it is a law that if the windshield wipers are on, the headlights must be on, even in the deytime. When I switch on the headlights in the daytime, the instruments are hard to read although the rheostat is turned to maximum brightness. Is there a way to increase the range of the instruments dimmer control? (maybe there is a resistor in series with the rheostat?) A schematic of the dimmer circuit might help me if you have one.
Have you rolled it up past the detent? When you do that the instrument panel lights go full on just like in daytime when the headlights are off.
