Once you remove the cluster from the dash, look at the top of the cluster. You'll see the white cover of those clear prisms.
If you really want to improve the lighting the clear prisms need cleaning, since they would have been lightly covered with black dust and crap.
Remove the 3 individual gauges from the cluster.
Go back to the white covers, I use a flat head screw driver and a hammer to pry out (and hammer out) the two white covers which are a bitch to remove, unlike those clusters on W124.
Once removed, the clear prisms can be washed as well as the white covers.
I use white spray paint to cover the black areas on the top of the cluster where the clear prisms sit (don't forget to tape up everything else, or you will have a lot of white spots on the cluster NOT NICE).
On the speedo housing, the plastic pieces that separate dash lights and indicator check light can be removed and painted white.
Basically all I have done is paint the path where the light would travel white, except the clear prisms.
When all is done just replace the 3W bulbs of the same wattage
I used hot melt glue to glue back the white covers (with clear prisms underneath) and assemble everything back together.
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