Hi All,
I've had an issue with the auto window down feature on my Cabrio that I'd like to get your input on. The window travels fine up/down, but when it reaches bottom it clicks repeatedly and wont stop unless I tip the switch. I can also replicate the sound by manually holding the down switch till tge window bottoms, then then clicking begins.

It sounds as if the worm gear in the motor was popping out of the tooth gear on the regulator. Operating the window with the inner panel and liner off, I can't see anything amiss. I dont see the reg gear moving, popping, nor do I see the motor moving in its mounts. Everything is tight, regulator mounts, motor mounts. The reg gear doesn’t look damaged, the teeth are sharp and clean.

Motor worm gear bad? I would have expected to see plastic dust, shreddings and certainly impact the window operation, but the window zips up and down fine with no delay nor odd noises.

Ideas?

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Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)

I have similar issues with two windows on my ‘84 300D. You motivated me to finally take a look at it. At this point it’s merely annoying, but it could get worse.

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Te futueo et caballum tuum

1986 300SDL, 362K
1984 300D, 138K

Wrong vehicle but on the rear windows of my 84 300D it was caused by the pot metal frame bending and the Motor teeth wearing the regulator gear teeth at an angle to the point that it skipped teeth causing a mechanical clicking sound.

As the other member said you won't know till you take a look.

You can get the new Door Panel Fasteners on eBay but if they come direct from China it can take 3-4 weeks to get them.

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84 300D, 82 Volvo 244Gl Diesel

Thanks for the suggestions. Will have a closer look. Im leaning to the motor gear teeth wearing at an angle. I noticed that the inner door skin steel does indeed flex/twist a little from the window motor torque when it bottoms out. Since this inner skin holds the reg and motor assemblies, that flex probably caused the uneven wear. Will have to take it out to see for sure.

Diesel911 did you replace the motor to fix? Do you know if the motor gear can be flipped around on its shaft as a potential fix?

Will have to confirm whether w124 front window motors are interchangeable across all models. If anyone knows, please advise.

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Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)

If this is 'auto' then it is not being told to stop. Check the limit switch. Meanwhile stop the window manually.

Thanks for the suggestion. Can you describe where the limit switch may be? I could not find one in the door, may have to look more closely, nor could I find a replacement pert or pert number for the limit switch.

Thanks

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Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)

I am not well versed in this issue. I assume if the window has a function to "auto down" it would know when to stop. Like a limit switch. It may rely on limiting current draw. or, what else could cause it to stop trying to go down? I dunno.

Again a different vehicle but on mine the motor gear teeth were hardened and the regulator teeth were not hardened. So there was no wear on the window motor gear. Let us know what you find.

What passes for a limit switch is inside of the motor (part of the motor itself) on mine. Apparently it is not entirely effective because the pot metal on both of my rear window regulators was bent. One was bent so much I replaced (which now is expensive).

In the pic is a 95 E300 window motor. The yellow circle is where the limit switch is.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

I'm not as experienced as most but my thought is the window comfort control module beneath the rear seat is failing to detect the 'extra current' caused by the window motor when it can't move further. This would cause the thermal cutoff that protects the motor to possibly click with it's switch action as it opens and closes.

From a little searching I believe the part # might be 124 820 48 26 supposedly that is the latest version.

If you can obtain one they're easy to swap out, just make sure you remove the plugs properly. First time I did mine, 95 E300D, all the wires came out. Took a while to put them back properly.

On mine the relay points are, in my opinion, too small for the window motor current and form deposits/wear after lots of use. I bought lots of new relays but don't know how to unsolder/solder such heavy components with a small soldering sucker/iron. Diodes, etc no problem.

For 124 820 48 26, if you can't find a used one that works, a company in europe supposedly repairs them.

One user said a non-covertible module will plug in but you lose the top button function.

You might want to search on 'E320 cabriolet comfort control module' and read a few posts on the problems.

The regulator or motor gear tooth wear will be clear on examination as will bending of the regulator.

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84 300D, 82 Volvo 244Gl Diesel

Searching shows a few links with discussions on the cabriolet comfort control module. Not much info and indicates that even used parts are very rare.

Even though your comfort control module might not be the problem. It might be a good idea to search from time to time for a spare. They are rare and can be expensive. Plus being used they might not function properly or reliably..

This site supposedly does an ebay world search. But does not show a complete list of what is advertised for sale at that time.

https://picclick.co.uk/?q=124+820+48+26+mercedes a search for Mercedes 1248204826

https://picclick.co.uk/?q=2028200926 a search for another comfort control module that would probably work but you might lose the 'convertible top' buttons function

picclick is sensitive to how you enter a search. A part might show up if you enter
"mercedes 2028200926" but may or may not show up if you enter "mercedes 202 820 09 26"

you could also search on " mercedes comfort control module" and if the ebay user describes it using those words you'll probably get a hit. But it would take a long time to search through them.

If it was my car I'd try to obtain one or more used spares of mercedes 2028200926 and be willing to lose the ' top ' button function. There are still new ones of this available but a used one would show if it was truly compatible. New ones are several hundred.

One site that discusses repairs:

https://forums.mercedesclub.org.uk/index.php?threads/124-module-repair.149271/