I have an '83 300sd that the dashboard lights do not work on. I recently got the car so I am pretty new to these cars. But I pulled the instrument cluster, checked continuity across the bulb and got continuity, the filament looked good, I did not check resistance though, but I am assuming that I have good bulbs. The turn signal indicator bulbs work, and everything else seems to work, but not the backlights.

Is there a switch or dimmer or something for these lights that I am missing?

Yes, there is a dimmer, the usual culprit. It's the same button as the trip odometer reset knob. Spin it back and forth, they may light up.

But now that the cluster is out, solder a jumper wire between the two posts. You'll be able to tell, it's a white box thing on the other side of that knob.

__________________
83 SD

84 CD

Do a search for rheostat. There's a good DIY for cleaning/repairing. Or there's the jumper solution.

or just spray some WD-40 on it while its on and keep turning it back and forth really fast a few times

Awesome, that makes sense now. I will try it out tomorrow. It was pretty simple pulling the cluster out. Thanks again.

__________________
1983 300SD Turbo Diesel Automatic