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Mono-Post Wiper Repair and Replacement
 
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Pelican Technical Article:

Mono-Post Wiper Repair and Replacement

Steve Vernon

Time:

4 hours4 hrs

Tab:

$15 to $50

Talent:

***

Tools:

17mm, 13mm, 10mm socket and wrenches, 5mm Allen, Philips screwdriver

Applicable Models:

Mercedes-Benz W124 (1986-95)

Parts Required:

Wiper arm, mono-post, wiper motor, mount, gaskets, trim pieces

Hot Tip:

Service the mono-post every two years

Performance Gain:

Working windshield wiper system

Complementary Modification:

Change cabin air filter

The mono-post windshield wiper on The Mercedes W124 is quite an ingenious system and can give you years of service when properly maintained. This article will show you how to maintain it as well as replace any components that may fail.

Begin by disconnecting the ground strap from the terminal on the battery and make sure it cannot come in accidental contact with the battery while working. You want to work on the wiper system while it is in the park mode. Having the motor accidentally move while working on it could cause damage to the vehicle and yourself.

NOTE: This article applies specifically to 1994-1995 facelift models only. If your car is 1986-1993 then the wiper head has an aluminum cover which requires complete removal of the wiper assembly, then further disassembly of the mechanism. If you try to "pry off" the aluminum cover you will just break it. Also, the wiper gasket shown in Figures 9, 36, and 37 are the late style, phased into production during late 1993 USA model year just prior to the facelift and all 1994-95 models. This late gasket extends along the entire base of the windshield. The 1986 through mid-1993 wipers do not have the attached/integrated gasket shown; 86-93 models have separate trim pieces along the base of the windshield.

Wiper Arm- The connection for the wiper arm is covered by a plastic trim piece on the mono-post.
Figure 1

Wiper Arm: The connection for the wiper arm is covered by a plastic trim piece on the mono-post. Begin by gently pulling both sides of the cover out (red arrows) and lifting the cover up.

Wiper Arm- Slide the cover back towards the base (red arrow) and remove it.
Figure 2

Wiper Arm: Slide the cover back towards the base (red arrow) and remove it.

Wiper Arm- Use a 5mm Allen key and completely remove the bolt (red arrow).
Figure 3

Wiper Arm: Use a 5mm Allen key and completely remove the bolt (red arrow). The bolt sits in a groove in the arm post so if you just loosen it you will not be able to remove the arm.

Wiper Arm- Lubricate the hole in the arm as well as the post.
Figure 4

Wiper Arm: Lubricate the hole in the arm as well as the post. Then pull the arm straight off the post (red arrow).

Mono-post Service- To remove the mono-post cover first pry up the edges away from the assembly (red arrows) then slide the cover forward and off the post through the hole in the cover (yellow arrow).
Figure 5

Mono-Post Service: To remove the mono-post cover first pry up the edges away from the assembly (red arrows) then slide the cover forward and off the post through the hole in the cover (yellow arrow).

Mono-post Service- With the cover off you can service the assembly.
Figure 6

Mono-Post Service: With the cover off you can service the assembly. The post rides up and down through the assembly (red arrow) and is driven by two small wheels riding on tracks (yellow arrows). Clean the old grease off of the post, wheels and tracks and apply a good all temperature grease.

Wiper Assembly- The mono-post wiper assembly (red arrow) can be removed with the wiper arm on or off.
Figure 7

Wiper Assembly: The mono-post wiper assembly (red arrow) can be removed with the wiper arm on or off. I recommend removing the arm to give you more room to work and eliminate some of the worry of damaging the paint.

Wiper Assembly-Begin by peeling back the weather stripping at the base of the plastic cowl (red arrow).
Figure 8

Wiper Assembly: Begin by peeling back the weather stripping at the base of the plastic cowl (red arrow). The weather stripping just pulls off the trim.

Wiper Assembly-Remove the windshield rubber gasket.
Figure 9

Wiper Assembly: Remove the windshield rubber gasket. There is a wide rubber gasket that seals out the elements from getting under the windshield and into the vehicle. Grab an end by the A-pillar (red arrow) and peel the piece back towards the wiper motor. There are two channels the gasket sits in so when reinstalling make sure they are both seated to get the full protection from the gasket. Remove the gasket from both sides until it is sitting free around the wiper arm.

Wiper Assembly-There is a small plastic grate under the wiper motor.
Figure 10

Wiper Assembly: There is a small plastic grate under the wiper motor. Remove it by pulling it straight up (red arrow).

Wiper Assembly- Remove the cover behind the battery by simply compressing it and pulling it out (red arrow).
Figure 11

Wiper Assembly: Remove the cover behind the battery by simply compressing it and pulling it out (red arrow). Note: the battery has been removed in this picture but you do not need to remove it to remove the cover.

Wiper Assembly- Remove the firewall rubber trim piece by pulling it off the firewall (red arrow).
Figure 12

Wiper Assembly: Remove the firewall rubber trim piece by pulling it off the firewall (red arrow).

Wiper Assembly-The plastic cowl on both sides of the wiper is made up of two pieces and held together by a plastic clip.
Figure 13

Wiper Assembly: The plastic cowl on both sides of the wiper is made up of two pieces and held together by a plastic clip. Remove the clips by pulling them straight back and out from the cowl (red arrow).

Wiper Assembly-You will need to remove the center piece by the firewall (red arrow) as well as remove the two cowl pieces (yellow and green arrows) on both sides of the wiper.
Figure 14

Wiper Assembly: You will need to remove the center piece by the firewall (red arrow) as well as remove the two cowl pieces (yellow and green arrows) on both sides of the wiper.

Wiper Assembly-On both sides use a Philips head screwdriver and remove the two screws (red arrows, one shown), then pull the trim pieces out.
Figure 15

Wiper Assembly: On both sides use a Philips head screwdriver and remove the two screws (red arrows, one shown), then pull the trim pieces out.

Wiper Assembly-At the end of both trim pieces by the A-pillar there is a drain spout (red arrow) that sits in a drain tube (yellow arrow).
Figure 16

Wiper Assembly: At the end of both trim pieces by the A-pillar there is a drain spout (red arrow) that sits in a drain tube (yellow arrow). Make sure the spout is in the tube when reinstalling or water will not drain correctly.

Wiper Assembly-Remove the center trim piece by unclipping it at the firewall (red arrow) and from the cowl (yellow arrow) on both sides.
Figure 17

Wiper Assembly: Remove the center trim piece by unclipping it at the firewall (red arrow) and from the cowl (yellow arrow) on both sides.

Wiper Assembly-Use a Philips head screwdriver and remove the four screws (red arrows) on both pieces.
Figure 18

Wiper Assembly: Use a Philips head screwdriver and remove the four screws (red arrows) on both pieces.

Wiper Assembly-Pull the plastic cowl pieces (red arrow) out from around the wiper motor.
Figure 19

Wiper Assembly: Pull the plastic cowl pieces (red arrow) out from around the wiper motor.

Wiper Assembly- After removing the vent trim piece from the right side you will need to remove the two Philips head screws from the larger trim piece (green arrows).
Figure 20

Wiper Assembly: After removing the vent trim piece from the right side you will need to remove the two Philips head screws from the larger trim piece (green arrows). Note: I removed the foam piece at the firewall for better pictures but you should be able to remove it without removing this piece. The foam piece gets very brittle with age and removing it almost always results in damage to it.

Wiper Assembly-Remove the piece from the vehicle (red arrow).
Figure 21

Wiper Assembly: Remove the piece from the vehicle (red arrow).

Wiper Assembly- You now have access to the wiper motor and assembly as well as the mono-post.
Figure 22

Wiper Assembly: You now have access to the wiper motor and assembly as well as the mono-post. The gasket will remain on the mono-post (red arrow).

Wiper Assembly- At the center base of the mono-post there is a rubber isolator and clip.
Figure 23

Wiper Assembly: At the center base of the mono-post there is a rubber isolator and clip. Use a screwdriver and gently pry the clip off the base of the mono-post (red arrow). Note: these clips are often missing and replaced by hose clamps.

Wiper Assembly- Use a 10mm socket and remove the four bolts (red arrows) holding the motor, mount and mono-post to the frame.
Figure 24

Wiper Assembly: Use a 10mm socket and remove the four bolts (red arrows) holding the motor, mount and mono-post to the frame.

Wiper Assembly- Remove the mount (yellow arrow) and assembly (red arrow) from the vehicle along with the gasket.
Figure 25

Wiper Assembly: Remove the mount (yellow arrow) and assembly (red arrow) from the vehicle along with the gasket.

Wiper Assembly- Disconnect the wiring harness (yellow arrow) from the back of the motor (red arrow) and take the assembly to your work bench.
Figure 26

Wiper Assembly: Disconnect the wiring harness (yellow arrow) from the back of the motor (red arrow) and take the assembly to your work bench.

Wiper Assembly- This photo illustrates the mount (yellow arrow), the trim and gaskets (red arrow) and the motor (green arrow).
Figure 27

Wiper Assembly: This photo illustrates the mount (yellow arrow), the trim and gaskets (red arrow) and the motor (green arrow).

Wiper Assembly- Use a 13mm wrench and remove the nut holding the motor to the swing arm (red arrow).
Figure 28

Wiper Assembly: Use a 13mm wrench and remove the nut holding the motor to the swing arm (red arrow). You will need to brace the arm from turning while removing the nut.

Wiper Assembly- Depending on the age of the arm and motor you may need to pull or pry the arm off.
Figure 29

Wiper Assembly: Depending on the age of the arm and motor you may need to pull or pry the arm off. There can get to be a little rust and corrosion on the spindled grooves. I used a tie rod remover and they separated right away.

Wiper Assembly- Use a 10mm socket and remove the three bolts holding the motor to the mount (red arrows).
Figure 30

Wiper Assembly: Use a 10mm socket and remove the three bolts holding the motor to the mount (red arrows).

Wiper Assembly- Remove the large rubber washer from the motor and separate it from the arm (red arrow).
Figure 31

Wiper Assembly: Remove the large rubber washer from the motor and separate it from the arm (red arrow). Before installing the new motor and hooking it up to the swing arm plug the motor into the wiring harness and run the wiper on and off to set the new motor in the park position, then assembly is the reverse of removal.

Wiper Assembly- Use a 17mm wrench and remove the nut holding the swing arm to the mono-post (red arrow).
Figure 32

Wiper Assembly: Use a 17mm wrench and remove the nut holding the swing arm to the mono-post (red arrow). You will need to brace the swing arm so it does not turn while removing the nut.

Wiper Assembly- A puller is sometimes needed to separate the swing arm from the mono-post (red arrow).
Figure 33

Wiper Assembly: A puller is sometimes needed to separate the swing arm from the mono-post (red arrow).

Wiper Assembly- With the swing arm off gently pry away the circlip (yellow arrow) and the washer from the post on the mono-post.
Figure 34

Wiper Assembly: With the swing arm off gently pry away the circlip (yellow arrow) and the washer from the post on the mono-post. You can now separate the mono-post assembly from the mount.

Wiper Assembly- This photo illustrates how the gear on the wiper arm base (red arrow) spins around inside the mono-post base (yellow arrow).
Figure 35

Wiper Assembly: This photo illustrates how the gear on the wiper arm base (red arrow) spins around inside the mono-post base (yellow arrow). Clean and re-lubricate this area.

Wiper Gasket- To replace the gasket first remove the plastic trim piece around the base by gently prying it up and sliding it off the base (red arrow).
Figure 36

Wiper Gasket: To replace the gasket first remove the plastic trim piece around the base by gently prying it up and sliding it off the base (red arrow).

Wiper Gasket- You can now release the gasket clip that holds the gasket in place.
Figure 37

Wiper Gasket: You can now release the gasket clip that holds the gasket in place. This is a factory clip and you will most likely destroy it during removal. Rather than install a new factory clip some people install the gasket with a Zip-tie. Installation is the reverse of removal.

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Comments and Suggestions:
lethiavan Comments: I see now too latefrom Kelly's contributions on February 5 this year that you shouldn't in fact use a club-hammer to "separate the mono-post assembly from the mount". Sorry about that. And on November 28 2015 somebody else had already identified the difficulty of reassembly if you have not marked the relative positions first. With the Internet the answer is always there somewhere - you just need to find it.
June 13, 2017
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
lethiavan Comments: A comment from London, England. I found this article very helpful, apart from the bit about prising off the monopost cover plate which, as others have pointed out, applies only to late-model W124s. My contribution to the party is this - at figure 34, before you "separate the mono-post assembly from the mount" which, incidentally, you achieve with determined application of a club-hammer, you need to mark the relative positions of the spindle and the mount, otherwise you will have difficulty reassembling them properly. After reassembly you should check the operation of the whole shebang before refitting it in the vehicle. For this purpose, rotate it through the complete cycle by hand. Plugging in the motor and testing it that way could do extensive damage if you have misaligned anything.
June 13, 2017
  Followup from the Pelican Staff: Thanks for sharing the additional info, tips and your experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
john1163b Comments: this question may be slightly off topic lol but my only issue with my wiper is the delay doesn't work constant low or constant high work fine but if you turn on for delay you get nothing
May 19, 2017
  Followup from the Pelican Staff: Test the signal out of the switch, if present, the wiper motor is the culprit. - Nick at Pelican Parts  
974970 Comments: How can you aling the wiper mechanism get the right angle position ?
Thanks
April 10, 2017
  Followup from the Pelican Staff: Mark the location on windshield with a crayon before removing. Then before installing wiper arm, turn wiper motor on then off, allow it to park. Then reinstall wiper arm in same position it was removed from. - Nick at Pelican Parts  
Roba Comments: Hello! Much thanks for those tips! This site rocks!
Can you tell me if the windshield rubber gasket is sitting only on the two tunnels or is it also attatched with some glue or something?
Thanku you!
April 4, 2017
  Followup from the Pelican Staff: It snaps into place. No glue. - Nick at Pelican Parts  
Streetballer Comments: I have a 1990 300E and had the wiper on high speed, then it stuck in position, stopped wiping, and I smelled something like burning. The fuse #2 was still operational as the wiper fluid was still able to spray. I guess its the motor that went bad. Has anyone experienced the smelling of burnt part when their motor stopped working?
March 27, 2017
  Followup from the Pelican Staff: Yes, as we call it in the industry, it let the factory smoke out! Mechanic humor haha. - Casey at Pelican Parts  
m Comments: Wiper was "frozen" to windshield and now won't turn mono assembly- 94 c220. Is there a way to 'tighten' the wiper to the linkage... The motor appears to work...
February 19, 2017
  Followup from the Pelican Staff: It looks like in Figure 27, there is a bolt to tighten but you must remove the wiper assembly. - Casey at Pelican Parts  
Kelly Comments: Oh I almost forgot. At installing you can get the arm in the base also at 90° but you need to push the rod full in!!Yellow arrow on pic
February 5, 2017
  Followup from the Pelican Staff: Thanks again. - Nick at Pelican Parts  
Kelly Comments: Update for 86-93 models!! I just finished mine. After figure 34, rotate the wiper arm to vertical center position 90°. Then you can pull out the arm from the base by hand DO NOT HIT WITH HAMMER!!! And after that you get acess to the 3 cover holder screw.as you can see on the photo.
February 5, 2017
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it. I will have the article updated. - Nick at Pelican Parts  
john1163b Comments: my only problems with mono wiper is delay doesn't work, and even with a new blade it only wipes outer edges of blade center of windshield is untouched.
January 7, 2017
  Followup from the Pelican Staff: The contact issue maybe the brand of wiper blade you are using. Try an OE. The delay issue is likely the wiper stalk, however it can also be the motor. best to check if the delay signal is being sent by the switch, if it is, the motor is at fault. - Nick at Pelican Parts  
GSXR Comments: Would you please update this article? The photo and description for Figure 5 only applies to 1994-1995 facelift models. This is both confusing and misleading for people with 1986-1993 models, which is probably the majority of readers. As described in the comments, the 86-93 wiper head has an aluminum cover which requires complete removal of the wiper assembly, then further disassembly of the mechanism. If people try to "pry off" the aluminum cover they will just break it.

Also, the wiper gasket shown in Figures 9, 36, and 37 are the late style, phased into production during late 1993 USA model year just prior to the facelift and all 1994-95 models. This late gasket extends along the entire base of the windshield. The 1986 through mid-1993 wipers do not have the attached/integrated gasket shown; 86-93 models have separate trim pieces along the base of the windshield.
December 20, 2016
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it. I will have the article updated.
- Nick at Pelican Parts
 
Andy Comments: 1998 230E, South Africa. Cover is aluminium Three Philips screws hold the side opposite the wiper shaft, can lift slightly, but will not budge further ? No more locating screws visible . Upon re-ssy, wiper arm moves from park position, to centre of windshield, then locks ! Will not move again, either way ?
Help please ?
August 3, 2016
  Followup from the Pelican Staff: Your vehicle may be different than US models. I don;t have any information to reference. - Nick at Pelican Parts  
Chaz Comments: Perfect. Thanks for your response!
April 29, 2016
  Followup from the Pelican Staff: No problem. - Nick at Pelican Parts  
Ossi Comments: I too have the aluminum cover, had to remove the wiper assembly to access first two screws, the dissamble the wiper assembly to access last two screws.
April 27, 2016
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Chaz Comments: Also, I cannot "move the wiper arm to the center" or see any kind of fasteners. The car has no battery or electrical system and the arm doesn't move freely.
April 24, 2016
  Followup from the Pelican Staff: If you have to move the wiper to get the assembly out, and there is no power, you will have to supply fused power and ground to do so. - Nick at Pelican Parts  
Chaz Comments: I re-read the comments and Nick's answers and I still cannot figure out what to do next. I have a 1989 300E early 1989 build with the aluminum cover. I have absolutely no access to the screws on the bottom side, let alone a tool that could reach them. Website will not allow me to post pictures, but I'm at the same spot where the guy pictured the knife blade in the crease which appears NOT to be the separation point.
April 24, 2016
  Followup from the Pelican Staff: Your vehicle may have a different wiper assembly. I responded in your earlier comment. - Nick at Pelican Parts  
Chaz Comments: Either I'm an idiot, or the instructions are not clear. I'm having the same issue as a few people above. I have the wiper blade arm removed after the 4mm hex nut but the cover does not "pry up" OR "pry away". I'm stuck at figure 5. No matter how hard I pull or pry, the cover does not budge. What am I doing wrong? Can someone spell this out a little more for me?
April 24, 2016
  Followup from the Pelican Staff: You may need to remove the entire wiper assembly, then disassmble the wiper pivot. - Nick at Pelican Parts  
Jeff Comments: I believe there are two types of cover one can be unsnapped as in the article. The second one has to be unscrewed after the entire unit is out of the car. I have an early car and removed the snap on cover. I also have one that I don't think is designed to unsnap. The snap on cover is a 1994, but it was built in 1993
December 19, 2015
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
Tim Comments: 1994 mercedes e320 wipers do not dock properly, mechanism greased, not sure what else to troubleshoot. I need to time the off and on of the wipers in order for them to dock fully, docking doesnt happen automatically
December 10, 2015
  Followup from the Pelican Staff: The issue is likely in the park switch in the wiper motor. - Nick at Pelican Parts  
Comments: Nick,if you have the aluminum covered "turtle head" cover. There are 3 Philips head recessedscrews that are under the "Turtle head" that must be removed before you can service the inside rollers and guides.Do not try to pry this,aluminum, cover off you will only damage it,remove the underside screws. The tricky part is in the reassembly, once you take the thing apart, getting the correct wiper arm angle/position so make sure that you mark or scribe the assembly arm positions before disassemble. Thank you for this very helpful site/photos.
November 28, 2015
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
RN Comments: Whats the right lube to use?
November 10, 2015
  Followup from the Pelican Staff: A silicone lubricant will work well. - Nick at Pelican Parts  
Phil Comments: Nick, I'm not sure we're on the same page here. I already removed the wiper arm as you demonstrated in your pictures. The problem is that I need to get to the rollers inside the mono assembly and, possibly, the gear set-up because it's not working correctly. Since I can't get the cover off, I'm assuming its screwed on from the bottom; thus I must remove the entire assembly to get access. In any event, thank you so much for your help, time, and expertise. I'll be ordering whatever I need to fix that along with other parts from you as soon as I can get it off which means getting the car from MY WIFE and figure out what I need. Thanks again for all you do. It's MUCH appreciated.
November 4, 2015
  Followup from the Pelican Staff: I attempted to describe the different procedures, as there are two. A repair manual may be the best option, as it will have illustrations. - Nick at Pelican Parts  
Phil Comments: It's a 92 300E 124 chassis. We also have a 92 400E 124. On both I cannot even admit a knife blade into the crack, and attempts to do so result in bright silver scratches that make the part look like aluminum. It is completely inflexible, like metal; it feels cold, like metal; and both pieces on both cars feel like they have recessed screws beneath the area that is supposed to "pry out". So I'm guessing they're both aluminum and screwed on. I fear I will have to remove it to find out, but I can't do that just now. Naturally, I was hoping for an easier solution.
November 4, 2015
  Followup from the Pelican Staff: Thanks for the info. Both versions have a bolt to release for the wiper arm. Then the wiper arm in moved to the middle of the windshield, fasteners are removed from the assembly, and it is removed as a unit. Once removed you can disassemble it. Let me know if this does it.- Nick at Pelican Parts  
Phil Comments: Nick, my cover appears to be made of aluminum, so it doesn't flex like the plastic wiper cover. It scratches bright silver and feels like it has two screws on either underside which I cannot reach without removing the entire assembly. Are you SURE this thing is supposed to be plastic? Would a better picture help?
November 4, 2015
  Followup from the Pelican Staff: What year is your vehicle? It may not come off until you can un bolt from the bottom. - Nick at Pelican Parts  
Phil Comments: I'm missing something on removing the mono-post cover. I cannot find a place to fit anything to "pry up". Where, exactly do you "pry up"? Mine seems solid except for a tiny crack that runs around the edge of the assembly. It admits not even a knife blade.
November 3, 2015
  Followup from the Pelican Staff: It says pry away, I think to better describe the process; pull the sides outward as you lift the cover up and slide it toward the wiper arm. - Nick at Pelican Parts  
zafer Comments: Thank you for sharing this information.
June 11, 2015
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
mike Comments: This is probably the best and most informative site I have found to help back-yard mechanics like me, thanks for the help.
April 24, 2015
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Mozza Comments: Einstein said "if you can't explain it simply you don't understand it". Your author must be related to him.
Never read such thorough and accurate instructions for motor repairs and I've been at it as an amateur for over 50 years.
Congratulations I'll be back.
January 2, 2015
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 

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Page last updated: Tue 9/19/2017 02:48:37 AM