I fixed the gear teeth on my rear drivers side electric window regulator on my 300D. I have a few junkyard regulators but their teeth were worn down or they were missing a couple of teeth. Had no way of knowing at the JY because I couldn't wind the gear out of the way of the motor pinion to take a look. My current installlation was starting to slip at the top of the travel and I figured it was time to restore the gears.

Here is the repair. TIG brazed silicon bronze caps on the broken and worn teeth. I then shaped them with a disk sander on the flat sides of the gear and a dremel fitted with a cutoff wheel for the teeth. The profile isn't perfect but it is much quieter now on the previously worn sections, and on the stripped section it doesn't freewheel anymore.

I took a look around and it wasn't clear if the new regulators are available anymore. My recollection was a W116 regulator could be modded to work on the W123. But, this was way more satisfying. Enjoy the visual smorgasbord.

Broken teeth. Worn teeth.




badly worn teeth



should look like this. these guys on the end don't get used.



cleaned up worn out teeth. these are noisy. they work but they growl as the window goes up.


braze on beads of silicon bronze.





grind down the beads with a Dremel and a flap wheel on my disk grinder. Easy and fast.



Not perfect but it works well. I have a slightly growly section in the middle but I think it'll get peened down by the pinion gear over time. I didn't make a tooth gauge from paper before I cut so the profiles are not perfect...I eyeballed it. The silicon bronze is a little softer than the steel. But not by much...those MB gear teeth are soft. Very satisfying fix for the afternoon.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles

I’m here for this and this is awesome.

Nice work Carl!

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1981 240D 4sp manual. Ivory White.

Very nicely done!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Silicon bronze, nice work.

I'm saving the link to this.

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84 300SD
85 380SE
83 528e
95 318ic

Thanks Shern.

Wish I had more going on with the cars. I should be happy that nothing has broken for months except for a couple of burned fuses.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles

I love it. That’s the difference between a mechanic and a technician! Most guys would’ve just got a new regulator. We were never allowed to do creative repairs at Benz. Parts changers!

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

On mine the reason the teeth were badly worn was the protometal frame was bent (rear windows W123).

I bit the bullet and bought one new regulator and unbent the other one.

Extreme rear window repair
Extreme Rear Window Regulator Repair,123

At the time the Arc Welder I had was unsuited for welding the teeth. I could do that now as since that time I acquired a flux core welder.

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84 300D, 82 Volvo 244Gl Diesel

very nice job...

Thanks guys.

Parts changers are good. . I would have loved to head over to Pelican and get a new regulator. Nothing wrong with that. Those days are long gone. I think rebuilding old parts is the new normal. More fixes on our cars are starting to look more like art restoration than conventional auto repair.

911, yeah the failure in my case was the same. The frame got twisted over and the gears started slipping and chewing on each other. The molded section is pretty flimsy but I guess it has lasted pretty long. Apparently this is a huge problem on C124 cars where the window is heavier. (ETA - hey just checked out your thread with the sheet metal plate you fabbed for your regulator. That is what is needed. That pot metal is too flimsy. It will bend again on my car. Too bad I have mine all buttoned up now. )

I had another bent up regulator and I actually cracked it while trying to straighten it out in my vise. Not sure how to weld or braze pot metal. This may be a valuable skill going forward. On my steering lock repair I accidentally turned one of the latch parts into a puddle of metal with my MAP torch. Not sure how to deal with die cast metal but a lot of the car seems to be made of it. It beats the heck out of plastic for durability but my cars are turning into metal dust at this age.

Silicon bronze is an interesting material. I got into using it after torch brazing some lock linkage parts with yellow brass. It may or may not be appropriate for this application because it is softer than steel. But if it lasts a few more years what can I say...the car is pushing 40 years old now. There is this desire to repair with the durability inherent in our cars. But today I’ll settled for this.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles

The claim is that alumiloy/alumiweld rods and a butane or propane torch will weld the pot metal or aluminum, but I never had success with those.

Looks like another company is Ultrafuse Aluminum Repair Easy Melt Low Temperature

Here is another that claims flux cored. Alumifix Flux-Cored Rods

Maybe the issue I have is no flux. The Harbor Fright rods have no flux with them.

This is the harbor freight products.
https://www.youtube.com/watch?v=7nWdmE93wP8

Pot metal and zinc die cast repair. Never seen one with flux.

https://www.youtube.com/watch?v=jwLuV00Psu0

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84 300D, 82 Volvo 244Gl Diesel

You do have to really clean the pot metal with a stainless steel brush. Just before attempting to use the specialty rods.

Personally I suspected you would have to do it frequently to get good at it. If I remember and it has been a long time. It solidifies harder than what you are using it on.

I have some of those Harbor Freight Aluminum brazing rods around from a prior repair to a radiator on another car. I may try those.

I can see that stuff not sticking if the surface isn’t cleaned or if I don’t use enough heat. What worries me about it is using it on anything that takes some cyclic loading. When I put two things together it is quite strong but if I keep fatiguing on it like a window regulator it may not hold up.

Well, I may give it a try. I have a junk regulator on the shelf that not only has teeth worn to nubs. It has a cracked aluminum boss right next to the motor mount where it bends. I managed to straighten it out but the crack got even worse. I degreased it and drilled out the tips of the crack. It’s A good throw away piece to practice on.

I kind of hate that Harbor Freight Alumiweld rod because it puts out this irritating smoke. I was choking for an hour after fixing that radiator.

The regulator casting is made from a die cast aluminum. It is a pretty high quality casting. It may be unfair to call it “pot metal”. I’m tempted to see what my TIG torch will do to it. Well, that is today’s project. I’ll get back later.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles

Well here is what I got. I decided against using the alumiweld rods. I had some aluminum wire lying around from a picture hanging project. I decided to try to TIG it with my DC welder. This was a longshot. DC and aluminum is a no go. I saw some videos on YouTube that showed you can kind of cheat and TIG weld aluminum with DC, argon and reverse polarity. This over heats the tungsten electrode so I welded in very short bursts. I decided it didn't have to be pretty. I just wanted to cover the cracks.

It was a cumbersome technique. I had to stop and sharpen up my tungsten several times. I also was limited to single tack welds. The arc also just wandered all over and didn't really behave. It needs a really short arc for things to happen...so I dipped a lot.

But, hey, it's welded! I ground things down and the cracks are definitely fused. Fun experiment. I think this casting is almost all aluminum. It welded pretty cleanly and didn't pop much like pot metal.

Enjoy the photos.

Cracked aluminum plate. Cast.


Cracked all the way through.


Poor man's DC TIG welds on aluminum. It's ugly but the cracks are fused shut.



Found more cracks and welded them. Ugly...it was really hard to control the arc.



Probably my best weld.



Ground down, cracks gone. Fused back together. Yes!



Nothing to be proud of, but the cracks are repaired. Nobody will see them in the door. Definitely AC is the way to weld aluminum but I had to try this hack. I don't weld enough aluminum to pay up for an AC welder.

The point of this experiment is that the castings are very weldable. They aren't really pot metal. At least the aluminum casting in the window regulator is not pot metal. And they can be welded using this awful reverse polarity hack in a pinch on a DC TIG with Argon. It looks like a robust fix.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles

All that matters is it worked.

I believe aluminum arc welding rods are used with reverse polarity. I was out of work when I bought my Lincoln arc welder, and I did not get the one with the variable amp adjustment and DC feature.
While it has served me faithfully since 1975 there has been times when I had wished I spent the extra and got the one with more features.

This is a pic from the internet. Looks the same as mine. They guy that owns it did what I did. He left the wooden board on the bottom from the crate it came in. Mine is like that but I put wheels on mine.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

That's a respectable repair! I would have never attempted that with DC so ya done good! I would have bet these things were pot metal. i like your sil-bronze idea for building the teeth back up. I would be fine with that for a seldom used back window. For a drivers window, I'm cutting new teeth. I can't believe no one is cutting that one gear out on a water jet. If anyone has that quarter gear out and wants to get it to me, I can draw it and see about blasting out a small run. That one is easy. The round one I can make on the mill in an evening.

Hey Diesel, have ya got an idea on fixing this sloppy gear before it eats my teeth?? It's not so much fixing it, it's reattaching it to the frame. I suppose I could just weld a blob on top of the posts.

https://www.benzworld.org/threads/coupe-window-regulator.3167499/?post_id=18976183#post-18976183