It is set at full brightness. I think the bulbs are getting old and just getting dim over time. I have replaced all of the other dash lights with LEDs.Have you tried adjusting the rheostat up and down? - the "dimmer" switch, or knob or dial that controls dash illumination level?
Kinda thought so. Do the switches come apart to get to the bulbs or can you get to them externally?The bulbs are replaceable btw but are a PITA to do so.