Last Saturday (the 20th) I replaced the power window motor in the driver side rear door of the 300D.

Holy overengineered Batman!

That motor looked like it could drive a midget motorhome! It must've weighed 15 pounds when I took it out! It felt like the weight of a a motorcycle alternator! Luckily I had a parts car or that motor wouldve cost me 250 dollars! My father was amazed at the fact that this motor was that insanely heavy and well built. My father and I also marveled at the massive steel tubing running through the inside of the door, which while impressive, made it a b!tch to get the different metal channel bars out of the way. 3 hours later following the Haynes manual (Installation opposite of taking apart...) the window works perfectly, and hopefully this 15 pound piece of German engineered motor will last another 30 years. I marveled at the amount of engineering these Kraut fiends put into a power window lifter as well as the safety tubing at the door, but also cursed them for overengineering such a seemingly simple device. In the end it was worth it.

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http://www.betten.mercedescenter.com...n_banner_1.jpg
1976 300D
190,000 Miles
Colorado Beige

1975 300D
Parts Car
78,000 Miles
Rustbucket
Also Colorado Beige

1984 190D 2.2 (Dad's)
156,000 miles
Champagne Metallic Clearcoat

That's because the window motor has to take a stalled conditon when you keep your finger on the button at the end of the window travel.

The windows have no limit switches so the motors must be overbuilt to take the additional current draw in a stall.

These motors are very durable. In fact, I've not heard of a motor failure in quite awhile. Usually it's the switch or the fuse.

Get the finger off that switch as soon as the glass reaches the stop (.01 second before........... )

I just replaced the passenger side front window motor on our 83 a few weeks ago, it was fairly easy to do. The old (original) motor was completely seized, I sawed it in half (was not easy) with a dremel to see the innards, the brushes were worn away and the spindle had corroded onto the magnets, overall it had died, from many raisings of the window. Ironically the regulator seemed to be brand new (no wear on it at all and it was shiny) so I think a prev owner replaced that, kept the motor, then the motor quit later on and he never bothered with it. We only paid $87 for the motor new off fastlane, not bad at all for a beast of a motor like that.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Those motors must put out some torque. I just repaired one of the rear windows on my "new" 240D. The PO told me that the PPO had the window propped up with a piece of wood. Anyway, what I found was that the motor was good but the regulator frame had been bent so the gears didn't line up. It appears that it had somehow jammed and tried to eat itself. Maybe the bolts holding the regulator to the door had come loose. All I had to do was straighten the frame, reinstall everything, and take out the piece of wood. I was actually able to fix something for $0.

Didn't know it entered a stalled condition. I'll have to keep my finger off the button as not to have to repeat that scenario on three other windows!

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http://www.betten.mercedescenter.com...n_banner_1.jpg
1976 300D
190,000 Miles
Colorado Beige

1975 300D
Parts Car
78,000 Miles
Rustbucket
Also Colorado Beige

1984 190D 2.2 (Dad's)
156,000 miles
Champagne Metallic Clearcoat

Don't feel bad. Until informed about it, most folks think that the glass has some type of limit switch to shut the current down. It doesn't. Bent up regulators, overheated motors, burned switch contacts.......................

I figured out that they didn't have limit switches shortly after I got the car and saw that the light would dim when putting up the windows and it got to the top. Ever since I remove my finger the instant a window is up or down, no fried motors for me! I also keep the rear switches locked so my friends can't mess with them if they're in the car and if they touch the front ones I whip their hands off the switch as soon as its up. People seem to have a habbit of pushing it, watching it go up, and then holding the switch an extra 5 seconds once its up or down....

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

So much for all the over engineering.

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85 300D 3 pedal. Current project.
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.

Well, as bad as it is and as little sense as it makes, it's an easy habit to form. A LOT of the new cars nowadays have an automatic shutoff that deactivates it all as soon as the window hits the top.

I don't abuse mine in that way and I still shred regulators almost routinely. I'm kind of sick of it. At the moment (knock on wood) all's been quiet on the window front for a while, but -- I've done the drivers side at least 3 times since we bought the 300SDL and the other 3 at least once each except maybe one.

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

This sounds like a great opportunity for a retro fit upgrade. if something could be attached to a new regulator assembly to eliminate "over closing", that might be a wise improvement.

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85 300D 3 pedal. Current project.
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.

A system is only as strong as its weakest link and these are a good example of a weak link design. The weak link in the window lift is the regulator. 95% of the time the failures in the mechanism is due to the regulators breaking - junk pot metal gears and frames.

As for the motor being designed to "stall" when it reaches the end - that's not why it is so strong - simply put it takes a lot of torque to raise and lower the windows as there is a lot of resistance in the channels and seals designed to keep the windows water tight around the edges - ever notice how many cranks it takes on a car with manual windows to raise and lower it all the way?

Those motors turn relatively slowly but have a lot of torque so they can lift the window at a reasonable speed. The reason the regulators break is because people don't stop pressing the buttons once the window reaches the end of its travel or accidentally hit close when they want to open the window (or vice-versa). Had the engineers at M-B been doing their work better they would have not designed a system that breaks simply because someone pushes the up button after the window is all the way up! An overload cutout would be an excellent addition and would save lots of regulators from the scrapheap.

I believe modern window lifts are mandated to stop and even reverse when they hit resistance for the sake of safety. That's why it is necessary to "sync" the windows so they close all the way in the newer models. In the W123 that wasn't a consideration (but should have been).

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Where was the plug for the harness-my 85 (now parts car) seems to run into the post--no end!

My Dad had a shop diagnose a bad motor on the 85 300SD even though it would work every once in a while. I just pulled the switch and saw a wire was just a little short of being fully inserted so it would contact until you hit a bump
and the either move in or out. Pushed it in and used a piece of quality electrical
tape to secure it until I have the time to take the switch apart and spread the contacts so they do not come out that way again.
Alan

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

Clearly the Rear "Pot Metal" Wondow Regulator Mounting Frames are not over-engineered.
Also the one I bought last year at $125 is not over $200 from the same source; the one the sent me was OE and had the Mercedes Star and part numbers on it.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

Most new car window motors use current sensing, or shaft rotation pulse monitoring. You can add current sensing with a module like DEI 530T, plus get a one-touch up feature. But I'd recommend you have very good rolling mechanisms, well lubricated... otherwise you'd get window stoppage half way up / down.

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Cheers!
Scott McPhee

1987 300D