i think i know what the problem is, but just wanted some feedback before i go and buy a new motor....

the passenger front window in my 300SD has been fagging out on me for the past few weeks and works sort of intermittenly....it can take ten minutes or more to get the window to creep down almost all the way...ive pulled the door panel off and lubed the tracks well and checked the sliding jaw...everything there is good....my only thoughts are that the motor is going bad and needs to be replaced...just figured id ask because i know how these cars can be....your wipers might not work, and its all because someone put 10w30 in instead of 15w40....sometimes i think these jokers are over engineered....thanks in advance for your comments

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1985 300SD 192,000miles...Astral silver/ Grey MbTex

1983 300D 194,000miles...White/Tan MbTex...my newest addiction

are you sure the switches are clean and making good contact? When mine were dirty the motor "did not work" once cleaned worked like new.
It is a tedious process but in my case was worth the effort.