To update:

I have replaced a few of the abovementioned bulbs.

1. To get to the bulbs behind the air vent thumbwheels, you must remove the center upper storage box, the center air vents, and within the opening you'll find two twist off bulbs. Didn't realize it at the time, but the bulbs I obtained from the dealer were 'clear' whereas the ones burnt out had an amber tint to them, so I took a magic marker to touch up the ones from the dealer, and I replaced.

2. The red and blue graphics between the center vents DO have a replaceable bulb. You must disassemble the center air vent assembly. If holding the vents horizontally on the top of it there is a center vertical shaft that holds the circuit board for the two buttons between the vent. All you have to is press from the bottom up and the circuit board pops up out of the air vent assembly. Once out you will notice the bulb (one bulb). I used a tweezers to pull it out and I replaced (bulb purchased from Auto Barn).

3. I bought tools to remove the instrument cluster from eBay. Cluster popped out without a problem. My instrument cluster is the 1992 - 1994 model that has a non digital odometer and a digital outside temp display. To my dismay, upon removal I learned that my version does not have a readily removable bulb for the outside temp display, but that it is soldered in, and it seems that to remove the bulb I would have needed to disassemble the entire cluster. Thus, I put it all back together and just left as it w/o backlighting for the temp display. Very upsetting!

4. At one point I needed to replace a faulty brake switch, and in doing so needed to remove the knee bolster below the steering wheel. While open, I looked to see if I could find any bulbs for the graphics above the headlamp switch, but was unable to see any way of gaining access to the area above the switch (where I believe the bulb(s) would be). I need another go at it from the top (removing the speaker and drivers side air vent - but that's for another time).

Only remaining issue, I cannot get the center glove box back in properly. I get it back in, I am able to press the button to open it once, but then the button no longer works and gets stuck in a 'de-pressed' position. Somehow I cannot seem to figure out how to get the whole system working again, which is not cool. If anyone has experienced the same and knows exactly how to replace properly let me know.

WBrian63: can you please clarify as to what hole you are referring to for putting in a drill bit? If the key is in the lock, where else is there a hole to put a drill bit? Is there any proper way of doing this w/o removal of the entire lock assembly?

Thanks, J.

Far as I know, there's no way to get the center glove box out without removing the lock cylinder. I've attached a picture from AllDataDIY - here are the instructions:

Glove compartment cover - open

Lock cylinder (arrow)
turn to right to 45° position with ignition key.

Lock cylinder (arrow)
remove, for this purpose insert a 1.5 mm dia. round pin with a minimum length of 45 mm into the hole at the circumference of the lock cylinder. This releases the catch on the lock cylinder and the lock cylinder can be pulled out of the housing with the ignition key. Observe installation note!

Ignition key
leave inserted in lock cylinder so that tumblers do not fall out.

Screw (arrow)
screw out at bottom of lock cylinder housing.

Housing (2)
pull out.

Control cable (3) and plug (4)
unhook and disconnect.

Housing (2)
lay to side.

Reinstall
in opposite order.

The installation note pictures are in the second attachment - here are the instructions:

When installing the lock cylinder ensure that the tab on the lock cylinder (arrow) engages in the recess on the drive lug in the housing.

Attached Thumbnails

   

Brian: Thank you for your very detailed and specific instructions. I will retry, and post the results. Best, JD.

Brian:

I tried again, but it just wont budge!

In the past, I have been able to get the upper glove compartment out without removing the lock assembly (as I have this past time w/ replacing the mentioned bulbs). The way that I do it is unscrew the rear two screws of the compartment, close the lid, put the lock in the locked position, and then basically wiggle it out. First pop out the left end, then sort of push the whole unit in and to the right (with the left end staying out) and in so releasing the two little rivits / latches holding the compartment to the lock assembly (on the lower right front of the compartment). Then the compartment basically pops out with a little more effort.

Hence, I did not previously have the need to remove the lock assembly, and I have been able to put it back in working order (in the past). However, this time something is wrong becuase when I get it back in, I am only able to use the button once, and then no longer - I can't figure it out!

Therefore, now that I need to remove the assembly to (I guess) do the job the way it was supposed to be done, but it doesnt want to come out!

Ive tried many times - with the master remote key, with the master plain key, with a thick paper clip, with a long nail. (both basically perfectly the size of the hole). It also seems that there are two points at which you are able to insert the 'pin' so that it takes - one at a point a little less than a 45 degree turn and one a little more than a 45 degree turn!!?? otherwise, precisely at 45 degrees the pin does not go in (the right amount) - no matter how hard I push. Other thing that I'm curious about is whether MB purposely designed the master remote key somehow that when it is insert into a lock it is freely able to bend w/o pressing the button - specially for this purpose - to access the little hole with a pin!?

You have been very helpful, and I do not see how else you may be able to assist - as the instructions and diagrams were as much as one can do, but I'm just not able to get it

Also, I do not believe I've broken the assembly becuase when the compartment is out - I am able to perfectly lock / unlock and push the button without it being stuck in the pressed position. Also, the compartment itself is functioning (when removed).

Really didnt want to take it to the dealer for such a nonsense simple issue only to be charged 1 hr of labor (130$). Or at that rate, even 1/2 hr!

Appologies for the long post. JD.

Good news everyone. So I replaced the bulb behind the graphics for the light switch / knob. If interested, take a look at what was posted on another forum: http://www.benzworld.org/forums/w140-s-class/1364695-w140-light-switch-graphics-backlighting.html. No need to remove the knee bolster!!! Also, I have replaced the bulb behind the red / blue HVAC graphics - so just a FYI - there is a bulb behind there if you dare to make the endeavor. Good luck.