I has issues w/ my power locks on my 90 sdl not working when below ~35F.
Once the wheather warmed the locks would lock but not open.
I opened the pump by the spare tire and it was wet.
I took the motor out cleaned, sprayed with water dispertant 40, said a few prayers voila...all is good.
I had trunk leak issues w/ the rear taillights leaking...somehow got into the power lock motor.

__________________
82 300D....went to MB heaven
90 350 SDL....excercising con rods