TIP: If you DO attempt to clean your switch contacts, be careful not to lose the little ball bearings (bb's if you will) that allow the armature/springs to rock back and forth.
It's best to disassemble them over a towel or something.
On my 85 300D I disconnected the 2 motors in question and used a jumper to apply 12V to the motor to verify that they would work both up and down. Come to find out that one of the motors had its harness cut inside the B pillar. When I asked the P.O. about this he gave me the deer-in-the-headlight look and said he had no idea what I was talking about. Since the motor worked I just rewired it from the center console switch. The other motor had apparently at one time or another had a short and the wire harness insulation had melted. I just rewired this part also.
How come it seems that 99% of the time it is NOT just a fuse?!
84 500SEL EURO 101K ( JUST LIKE MY 1ST WIFE. GLAD TO GET RID OF HER! )
85 300D 310K (sold)
90 350SDL 184K sold
83 300D 118K (sold)
88 300E 153k (sold)
93 400E 105K (sold)