Is this digital read out gauge LED or Liquid Crystal display? If it is Liquid Crystal display, you could have a polarization issue with sunglasses like robert graham was stating. That is because some glasses are polarized horizontally and others vertically. If you have that issue, sometimes you can turn your head at an angle and the display will be readable. However, if this is LED display then you either need a back-light display or a shade to be able to read it. Rarely is it a voltage issue beause such displays are usually setup for a 5 volt internal system voltage. So your supply voltage would have to be seriously bad. However, with that stated, I doubt it is your eyes like GA_boater was referencing. :facepalm:
Post a picture so we can see what you are dealing with. We may have better options. :noidea:
