How I made my instrument cluster so bright I actually need the dimmer...
 

My w115 was plagued with the fairly common problem of dim instrument cluster lighting. So this is what I did to fix it, keeping everything original.

1) I cleaned the glass thoroughly
2) I painted the inside of the cluster with gloss white spray paint. I even painted the circuit board where possible.
3) I replaced every bulb
4) I cleaned out any corrosion from the rheostat.

These four things made a remarkable difference. If you are bothered by dim instruments, this was an inexpensive solution. It did take a bit of time because I fixed my clock, restored my steering wheel, and fixed my column-shift gear indicator at the same time, but it was a fun winter project.

If you ever want more details, feel free to ask.

Pic??

When I replaced the burned out bulbs, and cleaned the rheostat, I also found it was more than bright enough for me. That being said, I like turning the ambient lighting down at night (in my Jeep, it is literally on the lowest setting at night - but it also has an LCD in the dash and the massive one in the console as well that put out quite a bit of light).

I will take a picture tonight to try to show how it looks lit up, but here are some other photos in the meantime. The first is the original steering wheel, and then you can see the results of my restoration in the second pic. I am pretty happy about that outcome. Total cost of the restoration was ~$20 (epoxy, spraypaint, and sandpaper) for the wheel and ~$30 for the steering wheel button/pad (I got lucky on ebay). The third photo is trying to show the cluster glass, but it is hard to tell that it is clean.

Attached is a photo trying to show how the instruments appear at night. How things look to a camera can be different than to our eye, but the photo is pretty fair. I didn't start the car for the photo, so perhaps it is a little brighter still when running off alternator voltage as opposed to battery voltage.

Anyway, I like these small fixes that one can do at minimal cost.

And please note that the clock is working! Whohoo!

Good job! I wish my steering wheel looked as good.

Just a caution to W201 and W124 owners seeking to brighten their clusters . . . do not use higher wattage bulbs. The extra heat generated will slowly but surely turn the bright cluster to dimmer than OEM when the cluster's plastic prism that reflects the bulb melts and discolors.

It took a little digging, but I believe these are the correct instrument cluster bulbs for a w114/w115.
MB part 0005446794
Osram part 072601012240

They are also referred to as Osram 33195 if you are buying a 10-pack or Osram 2821 if you are buying a single bulb. They are 12V, 3W, and have a wedge base.

Instrument panel brightening
 

Very cool! I will try this with my W116 350SE when the centre panel (HVAC) is changed and the tach/clock swapped for the dead clock.

Is that a dash cap I see there? My 72 250C has one crack on top of the dash, right by the glove compartment (like most others I've seen).
Thanks!
Ken

Yep, its a dash cap (which I am a little embarrassed of). I haven't glued it down yet and I still need to cut a hole in it for the speaker. I plan to cover the hole with the original speaker cover to make it look a little more original. It really is a remarkable piece of plastic. Without glue, it doesn't sit totally down near the window heater vents, but it does pretty good. I am sure with glue it would follows the contour of the dash perfectly.

My dash has tons of cracks, so fixing them wasn't very practical. My dash is the brown w115 dash, but I want to convert it to black with Sem color coat. So the black dash cap was just the first step in this process. My car will never be a show car, but little things like a dash cap do make it a more pleasant car to sit in, even at the expense of originality.

Been there, and melted that.