If it is only the climate control lamps that work intermittently, there may be a bad connection in the chain of wires that connects the illumination circuitry to the push-button unit (PBU). The PBU has two large plugs that carry all of the control signals including the illumination. A pin might be slightly corroded.

If the instrument cluster lamps work but the climate control and other console lamps do not work (check them all when it's dark) then you could be having a problem with a module that lives behind the instrument cluster. It allows the rheostat in the instrument cluster to control many lamps (lots of current) without burning out. The module contains a power transistor that takes the load off of the rheostat. The rheostat dims the instrument cluster lamps directly and everything else indirectly, through the module. To be sure, you need to make a list of which interior lamps work and which do not and then make sure all of the bulbs are good. This includes not only the PBU but all of the window switches, console switches, dash vent control wheels, etc.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970