There are 2 bulbs in the A/C control panel, then some transparent plastic is used to route the light to buttons and temperature dial. It's a very smart design, when you push down one of buttons, that button will get more light than other button.
You need to remove the ashtray (better remove the wood panel arround the **** lever first), the radio then the A/C control unit.
To access those bulbs, you have to remove all the buttons, be careful not to break them.
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.