how to replace heater illumination?

My V40 1999 ECC airco has 3 knobs for the heater. The temp knob suddenly isn't illuminated anymore. Yesterday I had the front cover disconnected. Now only 2 of the 3 knobs are illuminated? Contact problem or bulb broken? Where is that bulb located, what do I have to disconnect in order to reach it? Other posts explain only other types of heater consoles...

Some info and

i have s40, but presume they will be similar. i replaced my illumination bulbs over weekend, 2.60 from volvo main dealer. pull off the 3 dials, and the front fascia panel will come out, might be tight, i used flat screwdriver to wedge it out carefully, unclip the wires connection and there should be 2 brown like cubes, twist these to remove, these are the bulbs, simply replace and refit, and hey presto,

not 100% but i believe its to suck cabin air over the temp diode