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  #1  
Old 12-13-2002, 12:51 AM
shawnster
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how does the window motor know when to shut off?

The rear driver's window on my '81 300TD has some odd habits as of late:
1. it slips down so that I start to hear a whistle through it
2. it "thumps" rhythmically when going up or down
3. when all the way up the motor keeps going resulting in a thumpthumpthump until I let go of the button.

I had the door apart tonight and tried to visualize what was going on...I have experience replacing the front regulator on my car...but the regulator is tucked away and I couldn't extract it even after removing the retaining bolts. I did not visualize any breakage anywhere on the regulator.

what gives?

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  #2  
Old 12-13-2002, 09:41 AM
84300DT's Avatar
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fwiw

mine does the exact same thing shawnster (except on rear passenger side) - until i can check it out (when the weather is a tad better) i don't dare use it. at least it is staying up tight at the top.
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  #3  
Old 12-13-2002, 09:53 AM
Nate Stanley's Avatar
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The reason you are hearig the bumping noise is that the regulator and the motor gear have gone out of alignment.

This is because the regulator assembly is mounted on a die casting which warps over time as the window is raised against the stops. This die casting really should have been a steel stamping--

I have had some success in straightening the die casting. but be aware that the casting is brittle and dies not react well to radical changes during the straightening. The 3 mounting legs where it attaches to the door frame must be in the same plane. If you can tweak them into that condition. and at the same time get the motor and window riser gears to be in the same plane as well,
you will be able to reuse what you have.

There is no way to prevent the warpage of the die-cast frame except to use care in raising the windows, and don't let the motor push it too hard once the glass is in its up or down condition.

The rear regulators are simpler than the front ones because the fronts have that idler gear that adds one more element that must stay in proper alignment, and the 3 rear reguators I have straightened in my 2 W123 cars are fine after 2-3 years.
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  #4  
Old 12-13-2002, 11:26 AM
shawnster
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thanks to both...

so the gear which is stripped, txbill, is that the gear on the motor or on the regulator?

any tips for extracting the whole unit once I've undone the 3 retaining screws (actually 2 nuts and one screw)? It seemed that the channel was in the way...
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  #5  
Old 12-13-2002, 12:17 PM
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I replaced the regulator on a window earlier this year. The regulator is a metal framework that hooks the window and motor together. It has adjustable limiters to make sure the window goes all the way up and down. When it gets to the limit, it locks up and the motor can't turn anymore - I think it will keep trying if you keep your finger on the switch.
The thump thump in my case was a crack in the frame, the motor kept turning the gear which just kept flexing the broken frame. If you replace it, you will want to take the motor loose from the regulator, otherwise it is too big to easily get out of the door. You will also find that the genius who designed the contraption decided it would be a good idea to put the motor mounting bolts on the far side of the motor. Unless you have X-ray vision and can see though the door from the outside, you will just have to feel around for them. There are three. have fun!
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  #6  
Old 12-13-2002, 12:19 PM
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once the motor is out slide the window up and tape it there, then release the glass from the holder at the bottom and slide the lift mechanism back down. You should be able to get it out from there. at least it worked that way on my car.
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'78 300d
'95 volvo 850, wagon
'86 300sdl - engine out, maybe I'll have it rolling by June

whole bunch o' bicycles
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  #7  
Old 12-13-2002, 02:17 PM
Nate Stanley's Avatar
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In my limited experience with this, I have yet to see a stripped motor gear. if the regulators were as tough as the motors were. we wouldn't be having these discussiuons.

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2003 LS430 78K
2012 Kubota B 2320
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