S600L, 500CL, 560SL
Take the Side cover of the seat which holds the adjuster switch off. Then from inside of the seat cover the switch can be taken out n cleaned. Be careful not to brake the two tabs in front of the seat cover.By the way -
do you know how to get to the "0-5" switch to check/clean it (if can be cleaned at all)?
On the driver side it feels like not responding till in "0-4" position and then towards 5 it inflates very well.
Probably there is a way to remove this plastic side cover.