Repair your failed W124 window regulator motor (and maybe others too) - PeachParts Mercedes-Benz Forum

Chris_87_300D · #1 05-22-2012, 03:14 PM

I've seen lots of DIYs on removing, repairing, and reinstalling window regulators in the W124 - back and front. I haven't seen any on the motors. If I missed one somewhere, my apologies for the double post.

Three of my 4 windows failed, the drivers' side still worked. My conclusion is that they should be used regularly, not "saved", to keep in top working condition.

Back to the motors - there is a part on these motors that appears to be a safety circuit that breaks contact if the motor is put under excessive stress (such as holding down the switch when the window is fully closed or open). This component failed on all three of my windows by becoming corroded inside and no longer making sufficient contact to close the circuit. It's made by a company called "Otter", has "Made in Britain" embossed on it and is about an inch by 1/2 inch by 3/8 inch (from memory) and either black or white. It mounts inside the motor opposite the side where the power cable enters the motor. I found no reference to the part, part number, name, etc. on the web. If anyone has a lead on this part as a replacement, please post it here.

Fixing the motor is simple. Just solder a heavy copper wire (16 or 12 gauge solid copper house wire works fine) across these contacts to bypass the faulty part. See the attached pictures - the first is of the contacts (they're flat and a little farther apart than the contacts that are on the side where the wire enters the motor. The second is with the wire soldered in place (use electronics type flux to get a good connection). The third picture is what NOT to solder across or you'll short the incoming wires.

First things first - note which way the wire/motor is oriented with respect to the regulator so you get it back together with the wire on the right side. I am not sure but most likely it can be done wrong. This is more important on the front since the wire is very short.

You can remove the screws that hold the motor to the regulator (25 torx I think) and twist the motor enough to access these contacts. Solder away and you have a 50/50 chance that the motor will now run. If it doesn't, it's probably because the grease is all dried out. Using 12v leads, hold the regulator in a vice (or between your feet) and apply power while at the same time pulling the motor out. If you have the voltage + and - correct, and it runs, it'll back right out (or reverse the connections if you didn't get it right). You can then proceed to completely overhaul the motor and regulator gears. Note that there is no reason to remove the slotted screw that goes in the end of the regulator (where the end of the motor shaft will be).

Also note that by bypassing this part you are likely circumventing some sort of safety mechanism. I valued the motor working more than the "safety" feature and made the decision accordingly - you'll need to consider this decision on your car. As long as you don't have a 2 year old that is prone to holding down buttons and/or you keep the ice cream and cola out of the switches that might cause them to stick, I'd think that you'd be ok. Make this repair at your risk, however.

Back to the motor... If it doesn't back out or run, don't lose hope. Just keep working it by hand. It'll eventually free up enough that the gear will allow it to be pulled straight out of the gear (worked for me on both front and rear - only one of the 3 motors worked immediately upon the bridging trick). Worst case, proceed to disassembling the motor (with the sand filled hammer) and get the case off, then you can "unscrew" the worm gear by hand.

SIDEBAR 1 - Removing the motor / cleaning the gears on the BACK window regulators:

You can take the entire gizmo apart easily. Remove the 5 torx screws from the metal cover and remove the cover. Get a large sized spring clamp handy and carefully pop out the wheel that the cable is wrapped around. It is under tension. Keep it taut and put the spring clamp on the wheel so that the ends of the clamp are holding the wire on the spool so you don't have to worry about it unwinding. This would be inconvenient. Note that there are some little rubber bushings in the bottom (3) - don't lose these and make sure that they're in place when you return it to it's place at the end.

Now, take out the 6th screw that went into plastic. Very carefully, pry up on the outside of each of the places where the screws went (avoiding the gasket). The plastic piece will pop up with some effort. Carefully remove the fragile gasket.

Pull out the white gear. Note that it comes out in 2 pieces - a cover (which mates with the spooled up wire) and the gear with a rubber cover and seal on it. Remove these. Last, you'll see a thin washer. Remove it also. At this point, if the motor is still in there, you can remove it without effort. Clean the grease out of everything - motor, plastic parts, gears, etc. (I left the delicate cork gasket alone, though). Especially out of the place where the motor shaft lives.

If you want to finish the regulator, grease it all up with light grease (maybe lithium?) on the thin washer and bottom side of the gear. Also I used this light grease on the thin rim of the top part where it mates with the rubber seal but maybe silicone (dielectric) would be best here to preserve the rubber. I used wheel bearing grease to fill the teeth of the plastic gear and put a bit extra around where the motor shaft meets the gear after reinstalling the gear, Put everything back together except the motor. Alternatively, finish the motor, reinstall it after greasing it liberally, and finish the regulator last. Note that more isn't always better for greasing - if it's swimming in grease, it'll provide resistance.

SIDEBAR 2 -Removing the motor / cleaning the gears on the FRONT window regulators:

This case is metal and appears to be riveted together and not easily taken apart. Remove the motor by either backing it out under reverse power (if this works), working the regulator gear (carefully, with pliers for example) and pulling out the motor, or disassembling the motor and unscrewing the worm gear on the stator. Clean everything out that you can reach as good as possible. Then, once I did the motor work (below), I packed the worm gear with wheel bearing grease, inserted and ran it for 20 seconds or so, removed it and repacked it with more grease, reinserted, etc. about 4 times until the gear looked nice and greased up when I spun it around. A final packing of the shaft worm gear and you're good to go.

END SIDEBARS

Overhauling the motor:
To overhaul the motor, first remove the tape holding the wire to the case. Then hold the metal body of the motor with the motor pointing downward and (ideally) use a plastic sand-filled hammer to tap on the rounded end fairly forcefully. This will jar the stator and loosen up the white plastic piece, allowing you to wiggle it out, exposing the guts of the motor. Carefully remove the stator (main part of the motor, if I've got my terminology correct) and use brake cleaner and/or a wire brush to remove all of the oil and rust from the gear. I put a fine wire wheel in my drill press to polish it up once the grease was all out. Use fine steel wool on the ends of the shaft (not the wire brush) - the smoother the better since these are what holds the shaft when it's spinning. Also use contact cleaner or something similar to clean up the copper contacts on the shaft but be careful with them. I also used a small curved metal file to lightly sand down the brushes to freshen them up.

If you did a lousy soldering job in the tight space, now's the time to spiff that up. Don't get it too hot for too long, it's just mounted to plastic. Also, using an ohm meter test that one wire goes to one brush without resistance and the same with the other. Also verify that there is infinite resistance across the black and green wire with the stator removed. This will ensure that you didn't create (or there wasn't already) a short. If this isn't the case, it must be corrected or the motor won't run, fuse will blow, etc.

To reassemble the motor, move one carbon spring-loaded brush (in the plastic "electronics" end) to one side and put the stator through the hole at an angle to hold the brush in place against the copper contacts ring. Then use a small screwdriver to move the other brush out of the way and slip the shaft/stator back into place. Holding the worm gear and shaft tightly, apply a tiny bit of wheel bearing grease to the opposite smooth end of the shaft by the windings and reinsert it in the case. It'll stick to the metal on one side or the other - keep the plastic part in place while you work it back to where it belongs (grip the shaft tightly against the plastic and your hand will hold the plastic in place while you push it all back together. Make sure that you've got the wire entry point on the proper side of the case or it won't go back in. Once the motor is in, it should spin freely more or less although it won't be perfectly centered until it's back in the regulator housing. The plastic should be slighly recessed in the metal casing.

Center the motor shaft as best you can in the plastic top (without the regulator) and go hook it to the battery. It should spin fast and fancy free. If it does, retape the wire in place. If it doesn't, you might be SOL at this point but one possibility is the brushes. If the brushes are totally worn down and there's no spring left to them, you can go to a good auto parts store and buy new ones probably but I didn't have to deal with this issue... If you do have to go this route, and you can't find the correct size, buy slightly larger ones and just file them down to fit. There's not much else to go wrong with a motor except a short in the actual windings. One other thing to try is to take a razor blade and lightly cut/clean the lines between the copper contacts at the top of the windings - maybe some of these shorted across each other.

Last, clean and reinstall the rubber shaft seal where the motor shaft/worm gear enters the regulator, put a tiny amount of grease on the smooth end of the motor shaft that enters the regulator, pack the worm gear with wheel bearing grease, and reassemble. Double check your wire orientation vs. the regulator gearbox. If you put the gear in already, reverse the procedure of removal and hold it between your feet (or a vise) and apply power briefly when pushing it into place. It should "drive" itself in. If you didn't put the gear in, just slide it in. If the motor gasket is shot, you could use a bit of silicone/gasket maker to seal it. Seat it snugly and reinsert screws and tighten them down.

Put everything back together and give it some exercise to be sure that it works and at an appropriate speed. Just apply power, reverse, etc. to run the full course of the regulator. Of course, you should clean up and grease the remaining regulator parts also.

Pat yourself on the back for saving $150-$300 per window!

vstech · #2 05-22-2012, 03:36 PM

wow, thanks, this is great!

I think I will solder in some 10 amp circuit breakers instead of wire though!

Chris_87_300D · #3 05-23-2012, 02:07 AM

Thx, vstech!

I thought about the circuit breaker idea but I figured that the fuse under the hood would blow if the switch was held down that long and the fuse is easy enough to get at. There are also space constraints in the motor although I suppose that you could put it inline with one of the leads. My goal was to avoid getting inside those doors for another 10 years until everything needs to be regreased!

There may be a real part that could replace this but I don't know exactly what to look for and it'd have to be the correct size to fit in the small space. The part has the number 67H 084 stamped on it along with "Otter" and "Made in Britain".

See the pic for what this thing looks like inside. I think that when the metal gets hot, it bends the bottom (rusty piece to the left side by the contact leads in the pic) away from the base and breaks the connection. Since the connection is so badly corroded, it no longer conducts in the normal state. I wonder how many motors have been tossed because of that stupid part...

Pic 1 is the busted case and the guts below it. Pic 2 is bending the outside away from the contacts. It's really nasty in there. The back is all rusty also.

Graham · #4 06-16-2012, 10:01 PM

Interesting Chris - I recently posted about a similar "finding" when my W123 300D window motor failed.

W123 300D Window won't open
W123 300D Window won't open

I had several spare motors, so didn't bother with fix, but you are right in that jumpering the bad Otter device should make the motor run. BUT, it seem it is the only protection in the circuit to stop the motor once it hits up or down stop. And I am sure most of us hold the button down for a fraction too long on occasion!

It would be a lot more convenient if a cct breaker could be located in an easy to get at location. But taking door cover off or console apart is not too much different.

This company seems to have low cost self resetting cct breakers

TheDon · #5 06-16-2012, 10:08 PM

what about sluggish rear w124 window regulators?

Chris_87_300D · #6 06-18-2012, 12:32 AM

Ahhhh, so you also ran across the Otter! I didn't find anything when I googled it but there are numerous "otters" that come back with a search that would make it difficult to find what you really wanted... Nice job finding the actual part!

My 2 cents is that you're not likely to harm the motor by holding the switch for a few extra seconds - it would take that long for the Otter to get hot and break the contact. Where things are likely to go wrong is if you spill soda on your switch and it sticks down after you let up on the button and you don't realize it. If they're sticky, fix 'em. Absent something like that, these motors are pretty tough - mine looked really good after 25 years.

The circuit breaker idea is certainly interesting - it'd probably be easy to install on the front, there's already a screw-type mounting block there. I think that since you found the part, I'll just try to get some of those. I'll contact the company and post back.

TheDon - If you're getting a bright test light (strong 12 volts) where the motor connects (with the motor disconnected), take the regulator out, lube up the felt window tracks (I used a bit of silicone), and overhaul the regulator and motor as per the instructions above and elsewhere here and they should work almost like new. There are a few plastic parts that can get worn or broken (some can be replaced with some effort) and there is some rudimentary alignment w/ the regulator and the door that could impact it also. I'd take it out, clean it all up, grease it well and put it back together - you should be back in business.

I also took all of my switches apart and used a brass brush and ignition file to clean up the contacts. Clean all the plastic up to get anything that spilled out of there (but don't use any petroleum-based solvents). That job is much easier than the regulators - you might do it first.

Graham · #7 06-19-2012, 10:57 AM

Chris,
I saw these at Digikey. Haven't checked dimensions to see if they would fit in motor, but auto-reset version should work externally if need be:

Thermal Circuit Breaker Series 1610

Craig818 · #8 10-18-2012, 07:56 PM

Hi,

Rear right window on my 93 400SEL has been a prob for years so I searched out a repair on the boards and found my issue. After removing the door panel and drilling out the rivets, I removed the regulator to find the top pulley wheel gone and all the pieces in the door well. Put a new regulator in and up/down in the middle movement worked and sounded fine. Then the cast metal on the slide snapped. See attached picture. I thought the motor had a built in sensing system that stopped the movement at the top and bottom. Are there any adjustments that I missed? Any info and this fix would be greatly appreciated..
I have just replaced my second regulator and the same thing happened, it snapped the slide.

At wits end and greatly appreciate the help of any Mercedes genius'......

bigblockchev · #9 10-19-2012, 01:18 PM

Whenever I take one of these windows apart I usually find the motor is seized wedged in the shut position. There is a locknut at the end of the motor shaft with a slotted screw to adjust the end play in the motor shaft. I have found that if you loosen the locknut and slotted screw you can frequently get the motor to start turning by alternatly applying power in one direction then the other. A bit of WD40 or whatever helps to free things up as well. I haven't noticed the "ötter" bit in there but will look for it in the few motors which I have not been able to othewise repair. Cheers Dan

Chris_87_300D · #10 10-20-2012, 12:17 PM

Still working like new, no apparent ill effects from removing / bypassing the otter.

dieselmania · #11 10-22-2012, 12:07 AM

The cable pulled itself out from where it is held in by two metal prongs on my rear driver side. The end of the cable got wedged tightly at the wheel and jammed, probably opening the Otter device like you said because the motor does not work now. Has anyone tried to put the cable end back in and crimp it shut?

Mxfrank · #12 03-09-2013, 09:39 PM

Otter is a British company that makes sensors and switches. This is their website:

Home page

And this is probably the part you're looking for:

http://www.ottercontrols.co.uk/downloads/dl/file/id/5/pb_series_motor_protector_and_safety_cut_out.pdf

Graham · #13 03-09-2013, 10:05 PM

Quote:

Originally Posted by Mxfrank

Otter is a British company that makes sensors and switches. This is their website:

Home page

And this is probably the part you're looking for:

http://www.ottercontrols.co.uk/downloads/dl/file/id/5/pb_series_motor_protector_and_safety_cut_out.pdf

Yes, we established that earlier - see links in, I think, post 4 above. The problem is just exactly which is the right cct breaker and where are they sold. I seem to recall finding something similar at Digikey, but never tried it because I have spare motors.

merriwrj · #14 08-27-2013, 02:19 PM

Hi:

I came across the information on the window regulators, and have a question. When it was mentioned to repack the regulator gear body with wheel bearing grease, was all the old grease removed, I assume by spraying with solvent and blowing with air? Or did the repack go in on "top" of the old grease?

Chris_87_300D · #15 08-28-2013, 03:49 AM

It's old and hard or gunky most likely. I'd clean it out but it doesn't have to be spotlexx. Get any dirt out too and then grease her back up.

Good luck!