I'm having a real bad time trying to find a window motor for the front driver side. I did think that a 85 motor would work on my 84 190d, but the cog on the motor shaft was not long enough to connect with the groves in the regulator https://speedtest.vet/. After I sent the motor back I thought, what if I could pull the cog on the motor shaft up enough to fit in the regulator grooves. I think there was enough space to do this. Any body think this might work?

You did not say what was wrong with the original motor.

I had the passenger sided front motor freeze up due to sticky crud in the read bearing/bushing. Taking it apart and getting the bearing off of the shaft an cleaning and lubing what needed to be lubed fixed it.

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84 300D, 82 Volvo 244Gl Diesel

Also, there is a reed switch that gets deformed from holding the button too long… cleaning, or bypassing it may fix the original.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

One would think that bypassing the reed switch would put more stress on the Window Switch.

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84 300D, 82 Volvo 244Gl Diesel