Are my preset radio buttons ALL suppose to illuminate,also both temperate slides on 2004 Chevrolet Trailblazer

just bought vehicle. only buttons 1, 2 are illuminating at dark, along with only one side of the temperature slide for vents. Nothing in manual about illumination. Hard to see them at night.

1 answer
poss bad bulbs or circuit board inside.not sure if they are servicable in these units