Just bought 1997 e420 w210 with 132k on it for a great price(I Think)
of 2500 with it being pretty straight and clean.
it had some issues such as no blower for heat and the power locks not working.
blower was simply the resistor found one on ebay for $55 delivered, got it in 3 days and that took care of that.
the lock problem was the vac pump not working.
found moisture under the pump in the foam padding.
took pump apart and the underside of the board had corrosion in several places.
the top side of the board looked ok.
took a steel brush to the underside and removed any corrosion I could see.
reassembled and reinstalled in car, tested and sucess
locks now work like they should, and trunk release also now works.
so thanks for your description of what you did as it put me on the scent.
gemsbeme