There is a little light bulb deep in the control assembly # 9
09 BULB 12V 1,2 Part # 62111391777
You will need to remove the radio, pop out the three button A/C-Defroster button assembly, un clip the cables on the sliders and pop up the three knob control assembly.
Once you have it out, gently open it up and you will discover a tiny Xmas like bulb that lights up a clear plastic illumination bar that transmits light through the panel and knob.
My local dealer did not have the bulb, so I just soldered a new one into the old base.
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