Ok well as no one else has replied. I did this on a 190.
Basically, there were screws inside the vents, youll see them if you tilt the vents up and down. With those screws out, i think there were a couple of other obvious screws and then the whole vent pulled out. Then you can get at the bulb.
Had a look at inside the vents last night - no screw.
Just above the vents, there is a wood/plastic trim. Tried to remove it but only managed to get half of it out. I managed to see there are screws behind this trim for both the passenger and centre air vents. Will try again using some tools to get behind this trim and put it out.
If I can manage to get it apart, I will try to take some picture of it.
This is no help but I replaced the centre vent bulb on my W210 when I installed Comand - but I had half the dash out at the time so cant actually remember if there were any screws holding the vent in place. I think if you pull the centre wood facia away - released by two hidden screws above the ashtray - this allows the centre vent to come away
No screws inside my car's vents, buth there are some springy clips that I can move with a small screw-driver, but the vents stay put. I have also removed the screw just inside the glove-box door but everything is still held tightly in place.
Searched high and low but still couldn't fin any screws.
Nearly snapped the trim when trying to remove it.
Worked out how to remove the trim but still the vent wouldn't move.
I also tried the two little spring clips but still no joy.
Just in case you are interested on removing the trim.
1. Pry off the cover at the end of the dash of the passenger side
2. Remove the screw holding the tweeter cover and lift the cover slightly until it clears the trim
3. Open the glovebox and slide a flat blade tool underneath the trim and lever it out slower - this is held by 3 fasteners - spring tensioned - starting from the left air vent. You can hear them clicks as thry come out
4. Once you have released the 3 fastener, there are 2 more fasteners holding the trim in place. Slide the trim to the left towards the passenger door and pull out away from the dash
I hope this is useful.
By the way, enquired about the price of the trim - £45 !!!!!!!!
300-24, saloon and coupe, E300 24 valve diesel estate
There is an allen key in the centre near the vertical bar. Its hard to see and some upward and downward movement of the deflectors is needed. Take that out then the spring clips, gentley release them and pull forward.
If you are trying to replace the bulb behind one of the 2 dials for fan boost / airflow direction just grip the dial using pliers padded with cloth and pull the dial off the spindle. The bulb ,mini capless 12v-1.2w is in the centre of the spindle and is very fiddly to remove ; use a drinking straw with a spot of superglue ,allow to set then pull gently.