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Old 03-13-2010, 08:24 PM   #1 (permalink)
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Date registered: Jul 2008
Vehicle: 1998 C280
Location: Southeast Ohio
Posts: 60
Lightbulb Windshield Wiper Motor Replacement

If your windshield wiper sticks, stalls, slows down, etc, a very likely cause of the problem is a bad motor. The root cause of that is two gears inside becoming damaged. I do not know of a way to replace either of these two gears alone. Not to mention, this is probably a bad solution, for several reasons, the main reason being that a full motor replacement is cheap and easy. The part costs less than $100 and I've seen it as low as $75 brand new as of this posting (March of 2010). I bought mine from aiAutoparts on eBay for $80, brand new, OEM. Most other posters seem to have bought this part from AutohausAZ. Auto Haus' site says the part "lists" for $150 and they sell it for $96.21, and it was on sale for $91.40 when I searched it. They only list one part, but there are apparently two types of motor. One is for VIN serials through A644281, the other is for VIN serials from A644282. I honestly do not see why these can not be interchanged. Autozone, O'Reilly, and Advance Auto all list only one OEM replacement, but list two refurbished models. If you tried to get one of the refurbished models you have to return your current motor to get the core back, and you have to get the matching motor replacement. Seems right. Unfortunately one of the refurbished models is twice the price of the other. Both of the refurbished models cost more than the OEM model from these Autozone and gang. All three of these models from these stores cost more than the only part available from Auto Haus, AZ, and that is a new OEM replacement. The one I purchased was not for my VIN serial, BUT it matched the one I replaced, so someone may have swapped it out before I bought the car. In any case it appears these may be interchangeable. But do not take my word for it. You are advised to get the appropriate model for your VIN. I just recently installed mine, so given enough time to find out, I could end up regretting it. For all I know I'm replacing a motor the previous owner replaced 2 years ago and because it may be the wrong model it may go bad again. They both look identical in functional form, but have some slight differences in their casings. Here they are:

Name:  Motor PN_2028200408.jpg
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For VIN serials through A644281

Name:  Motor PN_2028202308.jpg
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For VIN serials from A644282

Tools Needed
  1. Socket wrench and extension
  2. 10mm socket
  3. 13mm socket
  4. 13mm open-ended wrench
  5. 5mm hex key
  6. Phillips head screwdriver
  7. Needle-nose pliers
  8. Pliers
  9. Something to hold and separate screws and nuts... please, no jokes.
  10. Brake parts cleaner
  11. Paper towels
  12. Two "work" towels (to drape over fenders)
  13. White lithium grease
  14. Elbow grease

Procedure : Removal
  1. Remove primary and secondary fuse box covers
  2. Remove wiper motor fuse and unplug motor
  3. Remove wiper blade
  4. Remove wiper arm
  5. Remove wiper transmission cover
  6. Remove the ventilation intake registers
  7. Remove fresh air ventilation duct
  8. Remove wiper motor and wiper transmission as one unit
  9. Separate wiper motor from wiper transmission

Procedure : Inspection, Preparation
  1. Check wiper transmission for problems
  2. Clean wiper transmission linkages
  3. Lube all contacting parts on wiper transmission
  4. Park new motor by itself, unattached

Procedure : Installation (not reverse of removal, exactly)
  1. Attach new wiper motor to wiper transmission
  2. Install wiper motor and wiper transmission as one unit
  3. Plug-in motor and install motor fuse
  4. Test motor operation
  5. Install primary and secondary fuse box covers
  6. Install fresh air ventilation duct
  7. Install driver and passenger ventilation intake registers
  8. Attach wiper transmission cover
  9. Attach wiper arm
  10. Attach wiper blade
  11. Wet windshield thoroughly and test away!!!

Get Started
Here's the long description with photos. The photos were taken mostly during installation at 1am. I apologize for the lighting, but you can see everything you need to. Also, keep in mind that since these photos were taken during the installation, they may appear to have some parts taken on or taken off out of order from my description. Also, my description does not match exactly the way I did. In hindsight I learned a better way to do this project and I am sharing that with you. Use the pictures as general reference.

Alright, let's get started. Get the tools I mentioned handy. Pop your hood and put it into the full vertical position. If you have never done this before, just look for the clips at each hinge, it's pretty straight forward.

Drape your towels over the fenders to avoid scratching them.

Procedure : Removal
Step One-Two: Remove the primary and secondary fuse panel covers; remove the wiper motor fuse and unplug the motor. The first cover is removable by hand by squeezing the clip. You will need a phillips screw driver to remove the second cover by removing five screws.

Step Three-Five: Remove the wiper blade, arm and the transmission cover. Remove the 5mm hex head bolt, then slide the wiper arm off the post. This can be kind of tough. Keep in mind there are springs behind the arm, if you pull the arm away from the windshield these springs will tend to push the block that is on the post towards the windshield. Pulling the arm off in this manner could risk damaging your windshield, even if you place something on the windshield to prevent this. Just be careful. Replace the 5mm hex head bolt into the wiper arm you just removed so you don't lose it. Now pop the plastic cover off of the wiper transmission, it pops off on the bottom and slides off the post at the top. It should come off with ease.

Step Six: Remove the ventilation intake registers. Each has three plastic clips you need to push down on while pulling the vents back. I used my thumb. As with all plastic clips you run the risk of breaking them if they are dry-rotted or if you use too much pressure or concentrated force. You shouldn't need a screwdriver to press on these, and using one could break them.

Step Seven: Remove the fresh air ventilation duct. It's all one piece. It has one plastic nut on each the driver and passenger sides. Remove the 10 screws across the back side of the duct, then look closely for all the clips on the front side of the duct. There's a bunch of them. I got all of them off by hand. You can roll and push the duct forward slightly to relieve some of the force on the clips.

Step Eight: Remove wiper motor and wiper transmission as one unit. you'll need to remove the shroud between the wiper transmission you recently took the plastic cover off of and the windshield. It comes out by hand. Two or three of the duct screws you've already removed were holding it in place to the duct. There are two nuts to remove, one clip to undo, and one bolt to loosen. This bolt doesn't appear to actually have a nut on the other side, a mere quarter turn and it is completely loose, if you turn it any farther than that you will damage the plastic ramp it tightens against. Remember this when installing later. First undo the white clip by hand, then remove the two 10mm nuts, then loosen the bolt on the rubber damper. To remove the assembly, tilt the whole assembly up while pushing back and slightly up to slide the flange out of the rubber damper. Watch your windshield here, you don't want to chip it.

Step Nine: Separate wiper motor from wiper transmission. Remove the one 13mm nut attaching the motor output shaft to the transmission, then remove the three 10mm bolts attaching the motor body to the transmission body. Pay attention to the orientation of the motor and the bolts for re-installation.

Prep and Installation post coming next. This post shortened due to image and character limitations.
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Old 03-13-2010, 08:51 PM   #2 (permalink)
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Date registered: Jul 2008
Vehicle: 1998 C280
Location: Southeast Ohio
Posts: 60
Lightbulb Windshield Wiper Motor Replacement Part Two

Procedure : Inspection, Preparation
Step One: Check wiper transmission for problems. With the motor taken off you should be able to move the wiper transmission around, see how it operates, note the linkage, movement and contact points, and check for problems. Mine was surprisingly stiff, but I have nothing to base this on, so it could have been normal. Take this time to take your motor apart to learn ya somethin'. Below is my motor taken apart, on the zoomed in image you can see where the worm gear was damaged. This then destroyed the plastic gear. MB engineers used the position of the plastic gear to detect the parked position, and not the position of the internal motor. This plastic gear's position directly relates to wiper position, so this problem won't cause your wiper to park in an odd place. The motor will keep running without parking unless it doesn't detect the park position for a given period of time. Then it will stop the motor anyway. So your wiper may stop in an odd place while the motor continues humming away. After a certain amount of time has elapsed the motor will just shut off. My gear was in good enough shape that I could actually move the wiper by hand in the places it got stuck to get it back to park.

Step Two: Clean wiper transmission linkages. Use break parts cleaner and get the old grease off that likely has grit packed in with it. Clean all the contacting points and surfaces thoroughly. This isn't your normal "lube job" on the wiper system. It could have failed due to problems in the movement. Give yourself peace of mind and spend the time to clean this well.

Step Three: Lube all contacting parts on wiper transmission. You can not see the moving parts inside part of the transmission. There's a small gear that rides inside a reverse gear as the wiper moves from side to side. This small gear being turned is what moves the elbow that is underneath and attached to the main post at its base. This creates the "M" motion the wiper makes. There are three holes you need to line up to be able to spray some white lithium down in there. If you get the post into the vertical position these should line up. Get your straw in there and spray away. Make sure you aim your straw around. Then spray all the visible moving parts. Move everything by hand and repeat your lubing as you see fit.

Step Four: Park new motor by itself, UNATTACHED!!! Make sure the car is off. Replace the fuse and plug in the motor. Have a helper hold it or get it secured somehow. Get in the car and turn it on, but don't start it. Run your wiper on intermittent and check that the motor runs, stops, runs, stops... etc. Put your wipers on slow, and check the speed and sound of the motor, remember the sound for later testing. Then put them on high and check again. Hit the sprayers to see if the motor comes on for a moment and shuts back off. Finally, run them on slow for a bit and then turn them off. Let it come to rest naturally, remove the key, unplug the motor and remove the fuse. You have parked the motor and are now ready to begin installation. You're more than halfway there.

Procedure : Installation (not reverse of removal, exactly)
Step One: Attach new wiper motor to wiper transmission. Position the motor and install the three bolts that attach it to the transmission. Your motor has been parked in the starting position, but now you need to set your transmission into the parked position before pressing the transmission's main arm onto the motor shaft. Since the motor spins constantly in the same direction and it is your transmission that makes your wiper move back and forth, you can choose to start your wiper in whatever position you like such as on the passenger side, up the center, or maybe at a 15.67 degree angle, whatever you like. To return it to "factory" settings there is an alignment mark on your transmission linkage to show you how everything lines up. That mark (or just a little bit of common sense) will show you exactly how to position everything before putting it back on the motor. I wouldn't worry about it being perfect. In fact, where I placed mine the arm wasn't straight with the alignment mark. Press the arm on and tighten the nut on the shaft. As you tighten you might get beyond the motor's internal friction point and begin turning it. This is where your 13mm open end wrench comes in handy because the socket will eventually get in the way of the linkage. I'd also advise getting the motor back into the parked position before plugging it in or it will start moving as soon as you turn the car on. Use your wrench to keep turning it in the same direction until it's back to the alignment mark. Don't try to go backwards, you'll just loosen the nut! You could also damage the motor and you'll be doing this replacement again in 18 months!

Step Two: Install wiper motor and wiper transmission as one unit. "Roll" the assembly into the damper bushing with the bolt, then let the other damper bushing (the one attached to the assembly) rest in the white clip, then align the bolt holes over the bolts on either side. Get the flange seated well in the damper bushing before tightening the bolt about 1/4 of a turn. DO NOT OVERTIGHTEN. This is not a traditional bolt. It merely turns on a plastic ramp. This is merely intended to absorb vibration. Clamp the white clip over the other damper bushing. I used my pliers on the wide setting and made sure they were clamping down on the very top. I could not get the clip to close completely by hand, it wouldn't click all the way in and was easy to flip back off. Once the clip is on right it should take a decent amount of effort to get it off by hand. The problem is you have to compress that bushing, and it's a bit tough to do by hand. Now put the two nuts back on and proceed.

Step Three: Plug-in motor and install motor fuse. Your new motor should have a rubber grommet floating down the wire, there should also be a similar rubber split-grommet on the vehicle. Route the wire through the one on the vehicle and install the one on the wire in the side wall of the fuse panel. Pay attention to the shape, it is molded to fit in one direction only. Pull most of the wire back out of the box through the grommet to make it easier to close later. Clip the motor power cord in, then plug in the fuse and get ready to test.

Step Four: Test motor operation. Get in your car and test. With everything bolted down not much can go wrong. Your wiper can not extend too far one way or another, Mercedes' engineers are just that thoughtful. It also can't go too far to one side or the other. This test gives you a chance to see that it stops in the right place. You will also want to pay attention to the motor sound and compare it to your earlier test. Now's the last chance you'll get to see if the motor is straining due to a faulty transmission. I also used this opportunity to add lube while everything was in continuous motion. Hopefully you haven't gotten overzealous and installed your wiper - if you have and you're testing with a dry windshield then you are putting your motor at great risk.

Step Five: Install primary and secondary fuse box covers. If the test was good, turn off your wiper and the car, then remove fuse 44 for safety. Put the secondary cover on, screw it in, and then place the primary cover back on.

Step Six: Install fresh air ventilation duct. This is the big piece, but remember, the shroud under the wiper transmission needs to go on first since 2-3 screws mount through it. Slide the shroud into place, then finagle the duct into position. Install the plastic nuts on either end, don't over tighten (they are plastic...) and then install the 10 screws. You may have to play with the alignment on each screw to get them in so don't tighten any of them all the way in before getting all of them started. After the nuts and screws are in place, clip all the clips on.

Step Seven: Install driver and passenger ventilation intake registers. When you removed these all you thought about were the three clips, but flip them over and look on the back and you will notice that they have clips there that slide underneath the plastic over the windshield. Get it all lined up together as you slide all the clips in at the same time.

Step Eight: Attach wiper transmission cover. It clips over it with the rod going through the hole at the end. That's it.

Step Nine: Attach wiper arm. Remove the 5mm hex head bolt. Slide the arm over the post, and then install the bolt back where it goes. Tighten that down. Again, keep in mind this thing is spring loaded and it'll take a little pushing to get it on right. Attach the wiper blade.

Step Ten: Wet your windshield and test. Oh... reinstall fuse 44, first. You're done. Clean up, put away your tools and take her for a test drive.

You can simply remove the wiper blade and arm and then that plastic cover to periodically lube it up again. If you run your wiper and try to stop it in the middle you can even lube the inner gears. Take the vents off again if you feel like lubing the linkages in the back.

If you have any troubles I've subscribed to this post. I encourage you to ask questions here, not through PM. The whole point of a board is to share your knowledge. I created this post because all of the others were lacking in one area or another and people kept "+1"ing a post that was 3 years old. Hopefully this covers it... it IS long enough, don't ya think?!

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Old 03-14-2010, 09:47 PM   #3 (permalink)
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Date registered: Mar 2010
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Jonzbenz I just wanted to personaly thank you for this posting in detail although I have not taken mines a looses it seem the motor is working but the arm or tranmission part is not moving the blade but i can see the motor moving the part behind the arm machinism I just have to take it off and find out why the arm is not moving I thank God for you and your posting and look forward to doing the work my self because i to was quoted about a grand also I am a cook and not a machnic but I learning to be patient and to look for posting like your again thank you Dar
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Old 03-14-2010, 10:55 PM   #4 (permalink)
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Date registered: Jun 2009
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Hey man, thank you so much for your post it has helped so much!

My cars wiper is hitting the plastic on the passenger side. It appears that it doesnt go far enough on the driver side and then goes like an inch too far the other way and hits the plastic everytime.

Would this be fixed by simply loosening that 13mm nut and adjusting it?
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Old 03-15-2010, 04:51 AM   #5 (permalink)
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Location: Southeast Ohio
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dar, no problem. I hope this post and the photos help some. If I understand what you are saying correctly, you probably need to purchase a new linkage system, or what I referred to in my post as the "wiper transmission," since that was what my dealer called it. It's basically everything that isn't the motor - including the piece that actually moves your wiper blade left-to-right and up-and-down. If your motor is spinning, and you can see some of these linkages moving underneath, but your wiper isn't moving, then I can almost guarantee you that you'll need the "transmission" part. Check this video out to see if it helps you at all: My Motor and Transmission Test.
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Old 03-15-2010, 05:30 AM   #6 (permalink)
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No, loosening the nut I mentioned and moving things around will only change the angle at which your blade parks. It will not change where the wiper goes in and out and will not solve your problem.

Try this for more reference material, it has lots of links. Follow them all and you will learn a LOT, but you're going to have to get your hands dirty to truly understand a lot of it.

That's where I started, and somewhere along the way someone mentioned something about your wiper hitting the trim on one side of the windshield. The part that does this is enclosed and not typically serviced, even when doing this repair. I suppose if the inner gear's and out gear's teeth skipped a tooth or two, OR if the "cogged wheel" mentioned in the pic below slipped on it's shaft, then the relationship between angle of the wiper and it's length of wipe would be changed, causing it to get longer/shorter in the wrong place.

The next photo below is just wrong. If you want to change your park position slacken nut 2, NOT nut 1. Slacken nut 2, pull the plate off, move the wiper where you want it, then put the plate back on the shaft and tighten nut 2 back down. There is no reason to ever adjust nut 1. There is an alignment mark on this part that shows you where the factory put the park position.

Please be careful messing with all this, especially once you hook power back up to the motor. If the motor is not parked it will move... just like when you shut your car off and leave your wipers on. Even if you were to turn the control stalk for the wipers to off, the next time you turn your car on, before the engine turns over, the wiper will try to go to it's park position.

Just read all this stuff, take your time, get to know what's going on, and then get to work. You'll learn 90% after you start taking everything apart.

Good luck!
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Old 03-29-2010, 05:14 AM   #7 (permalink)
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Originally Posted by JonzBenz View Post
The next photo below is just wrong. If you want to change your park position slacken nut 2, NOT nut 1. Slacken nut 2, pull the plate off, move the wiper where you want it, then put the plate back on the shaft and tighten nut 2 back down. There is no reason to ever adjust nut 1. There is an alignment mark on this part that shows you where the factory put the park position.
Hi JonzBenz, my name is Dec, I am the original author of the 2 pictures in the above post #6 .

I thought I should let you know that the pictures A and C below had been revised, you must have missed them here in post #12 page 2… Setting up Front Windscreen wiper - Page 2 - Mercedes-Benz Owners' Forums … the are significant in that the deal with alignment markings on the rear of the mechanism, as you can see the are not present on your copy of the pictures.

I just wanted to clarify what you say about Nut 1 being the incorrect nut to make adjustments to the park position.

When a new (pre parked) motor is installed via its 3 bolts, the short motor arm or as you describe, the plate, is attached to the new motor so as it is aligned with the V mark in picture A, below, this V mark represents the park position of the motor.

In most cases there will be no need to make any adjustments at Nut 1 if a new motor is being fitted PROVIDED the alignment marks (picture A, bottom left) are correct.


If a new motor is not being fitted but the wiper blade is not parking exactly where it is supposed to at the bottom of the screen on driver side, then adjustments can be made at Nut 1, again PROVIDED the V alignment mark at Nut 2 is correct and the motor has already been pre parked.

The park position of the blade can be lost if the wiper were to be switched on when the blade is frozen/snowed to the windscreen resulting in a loose Nut 1 or 2 slipping and causing the blade to park in the wrong place when the wiper is switched off at the stalk.

The intent of picture A is to illustrate the position of BOTH sets of alignment markings when a new motor (pre parked) has been installed or when the wiper blade fails to park in its correct position. The alignment marks are there for a reason and shouldn’t be ignored.


Last edited by c180w20294; 03-29-2010 at 05:26 AM.
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Old 03-29-2010, 07:36 AM   #8 (permalink)
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Date registered: Mar 2010
Vehicle: 1997 C230 184K
Location: Berkshire County Massachusetts
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Nice. Have you the one for Headlight Wipers?

I am a new to this forum C230 1997 new Benz owner. I have been able to clean it preliminarily and put in anew head unit. I have headlight wipers and wonder if you have the same how-to for those I guess semi-useless units?
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Old 03-29-2010, 08:54 AM   #9 (permalink)
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Location: Southeast Ohio
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Thumbs up

Originally Posted by c180w20294 View Post
I just wanted to clarify what you say about Nut 1 being the incorrect nut to make adjustments to the park position.
The park position of the blade can be lost if the wiper were to be switched on when the blade is frozen/snowed to the windscreen resulting in a loose Nut 1 or 2 slipping and causing the blade to park in the wrong place when the wiper is switched off at the stalk.
Touche, good sir. This is absolutely correct.
I remember reading a little discussion about it on your original post, but at the time I hadn't pulled everything apart and wrote it out of my mind as something I didn't understand. I'm also not sure my assembly had the alignment mark your pictures show on the wiper housing, I only know for sure of the one near where the motor attaches. I also know there were two ever-so-slightly different versions of the motor and assembly manufactured. This may be worth noting for anyone tackling this in the future.

My apologies for discrediting you originally. I looked at things wrong and didn't anticipate nor remember the discussion about Nut1 becoming loose and allowing the alignment of the wiper arm to change. I'm glad you corrected it here with updated photos and a thorough explanation! MUCH appreciated!!!

Originally Posted by MartySzy1 View Post
I have headlight wipers and wonder if you have the same how-to for those?
Sorry, I do not. Others may. Make sure you search thoroughly to see if others have posted about it before adding a new thread, though. Also, asking a question not exactly related like this can sometimes give you false-hope of receiving an answer. I happen to check all my posts, others do not, and most do not like a thread turning into a multi-topic discussion.

But, if you do find any threads about your problem, and/or if you create a new one, particular if you have the fix for it, feel free to come back and post a link here. It would be a decent place as I'm sure anyone searching for that repair will get this thread returned to them as well. Also, look through the common problems sticky. It's messy and full of loads of junk, but the gems that are in there can be worth it. You can try doing a search just on that thread alone.

Good luck!
1998 C280 Silver

Owned by an Auburn University '05 EE Grad

War D*** Eagle!!!

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Old 04-21-2010, 08:32 PM   #10 (permalink)
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Thanks for the great write up. and the important tips on parking the motor and the transmission. Installed it without a hitch.
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