'91 560SEC, '91 300SE (sold), '98 Yota, '02 S-10 Hauler
After the US Army spent $25,000 beack in '79 to train me I'd first use spray contact cleaner shot from underneath (out and away from the glossy panel of course ) shake it off and spray again, let it dry while running the thumbwheel back and forth, then snap it apart for just a dab of dielectric grease. I did the same with window and seat switches and work better than new. I know of at least one rear window switch I'll have to clean, can't even move it at the momentspeaker fader R&R
Just installed a new speaker fader so I thought I would take apart the old one. Found out it is extremely easy and you should be able to repair yours. The two side panels just snap out. make sure you lift from the bottom only, not stressing the top, if you look closely the side fits under a ridge on the top.
the two sides just pop off. I found hard crud built up on the metal slider wheel, the traces all looked fine, I gave them a quick brass wire brush clean up.
last picture show I snapped off one of the top lips, it is probably still usable even like that. There is also a tine spring on the side with 3 prongs dont lose it.