87 XT digital dash brightness

[SiriusBlack]

I have a digital dash in my 87 XT turbo, and it seems really dim and hard to read in the sun. The dimmer switch only affects how bright it is when the headlights are on. Does anyone know how to make the Digi dash brighter when the lights are off? I'd really like them to be easier to read in the daylight. 

Thanks in advance.