Lim, on W124 instrument cluster, the bottom row of bulbs, there is a red capped bulb.
This is not a bulb but a fuse.
Do yourself a favor and modify this while you have the cluster out.
Remove the red bulb and solder a 16 ga. twin lead wire to both terminals of the bulb holder.
Replace in the housing without the fuse, then route the wire behind and down the instrument panel and under the floor mat or insulation.
At this end of the wire solder a mini-blad fuse holder and use a mini-blad fuse of the right value.
Now should the fuse blow and let's pray it doesn't, you can easily replace it being under the floor mat not in the instrument cluster.
If I seem vague about values, they are referenced in my Shop Manual Electrical and I,m too lazy to go get them, but you will do fine by following the bouncing ball.
Happy Trails Beep Beep from Houston!!!
Donald, El Cheapo