On my 560SEL (1989) when I roll up the driver's window I get a very loud bang and clatter at the end, just when the window reaches the top. It seems like the motor is not shutting off, making the top of the window hit the frame hard, and the wanting to continue running, making the gear or something inside grind and creating a snapping sound in the door.

This is not the standard slider failure (I already bought a replacement in the case I have to go inside and take the mechanism apart - might as well put in a new slider!). My question is if anyone else had this happen, and if I should look at the electrical side (i.e. motor shutoff) instead.

Thanks!

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Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

I've had to repair all four window mechanisms on my W124 over a period of several years. The rears had failed slider jaws, and the fronts had trashed the gearbox attached to the motor. The odd noises you are hearing may be due to the gearbox going south.

Unfortunately, you can't buy one new without having to purchase the entire window mechanism. Your best bet would be scrounging for a used mechanism...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

Has anyone ever repaired one of these gearboxes?

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Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

Update - looking at another site, this seems to be the problem:

"Window operates ok except for one hell of a clunking/grinding/banging noise when it gets to the top. REALLY common on W123 cars, especially rears. It's probably because you ignored the fact that the bolts holding the riser to the door were loose. I've even seen them crack the inner door shell. The torque of the motor twisted the beejezus outta' the cast bracket part of the riser assembly....and it cracked. (I've got used ones that aren't....)"

Go this from http://www.msdra.com/mercedes_power_windows.htm

When I am careful closing the window, i.e. I am letting go of the button just as it reaches the topmost position, everything is fine. Has anyone dealt with this one on the W126?

Anyhow, it looks like I will have to go inside the door this weekend and see what is going on...

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Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

This happens on the W126 coupes with some frequency--the anchors for the window mechanism are insufficiently bolstered for the thin sheetmetal door skin and it tears. Some epoxies might work rather than risk welding. Reference:
http://db.mercedes.cx/sec/200407/26/0040.html
http://db.mercedes.cx/sec/200301/26/0000.html

Cheers, Andrew Seidel

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86 560SEC
85 500SEC Lorinser
83 300D Turbo
75 240D

Hopefully loose bolts are your problem but when my W124 started making that noise it wasn't long before the regulator gear stripped. The sound was the motor gear teeth jumping over the regulator teeth.

Beautiful, isn't it?

John Plut, you were dead on target.

Now comes the question: What caused it? Do I simply replace the armature and keep the motor and gearbox, or was this caused by a failure of the motor to disengage, i.e. I need a whole new assembly (in which case I am going to a junk yard)?

Any help and enlightenment would be much appreciated!

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Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

This is a common problem I now hear. I ordered a new regulator. There are after-market ones available for $50. Just bought one.

Thanks for all the input!

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Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

The operation of the motor/regulator is not a good one.........by design. There is no electrical limit switch in the system. So, if you let the window ride all the way to the top of the frame, the motor is strong enough to bend the hell out of the regulator and highly stress the teeth in the regulator. If you do it often enough, the same teeth in the regulator take a beating and they finally wear to the point that the pinion on the motor will spin freely at the top of the travel. This now compromises the capability to lift and lower the glass.

You'll need a new regulator...........and some future skill at operating the lift buttons. Don't run the window right to the very top. Develop the skill to leave 1/16" above the glass............the window won't leak and the regulator will last forever.

I had gathered as much by now. I'm not the guilty culprit - I just have had this car for the last 20k miles (out of 117k)!

But I have to say - now that I found a new one for $50, this is not the worst thing that can happen. Wish I knew how to weld though - I think it's a trip that several people on this forum actually re-used the old one, after welding a piece of metal in place and filing new teeth out of it!

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Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

That would be me, for one. All I did was mig weld the teeth area where it was ground off, like in your picture, then grind/file new teeth. That was in Oct 2005, and it's still fine. The job took less than 3/4 hour, not counting disassembly/reassembly.
You might try a buddy with a mig, or a local shop that could do it. The welding is only a 15 minute job......

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1986 560SL
2002 Toyota Camry
1993 Lexus

I don't believe such an approach is conducive to a long term fix. The shape and fit of the teeth to the pinion on the motor is important. It's likely that both the new teeth and the teeth on the motor will fail in the future with the welded approach.

A replacement regulator is the way to go.

For $50 at least you know it's done right and should last the next 100K miles...

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Of course self-machining is far more risky. I just liked the self-sufficiency of that sort of repair.

But no - event though this is not an OEM part I ordered (it's after market, the OEM is around $170, and this is $50 new), I still think this is the better solution. I get to re-use the old motor.

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Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)