Crazy windshield wiper

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IRONHEART's picture


GENTLEMEN: Please tell me that someone else with a 93 300E has experienced the following.
I will be driving down the road and the Wiper comes on for a few swipes then goes off on it's own..all of it's own accord......

If I hold the Switch out in the off position it stops actuating.

Is it time to replace the Signal Indicator/Wiperswitch ???

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rogo's picture

Re: Crazy windshield wiper

No, it's time to give your dealer USD$1,500 and he will install a new transmission..............................................or clean and grease it.

The following is as much as or way more information than you will need to lube your WW transmission. The process is further shortened if the plastic cove is the flexible type.

If so, use a seal pick at 5 and then 7 o'clock to raise the cover after the arm is removed. You can then simply clean and grease the transmission and put it back together and spend the money you saved at El Conquistador.

Message: 2
Date: Sat, 13 Aug 2005 18:09:17 +0930
From: "Anthony Tugwell"
Subject: [MB] re: W124 Mono-wiper

Update on Repair Procedure for Mono-Wiper Assembly
Mercedes-Benz W124 chassis pre-1994
In the hope that it could benefit others, (those without professional
Skill and training principally), who might want to carry out a repair or maintenance procedure on their own mono-wiper unit, I ve taken the
Liberty of compiling information from other sources and adding my own
Information gathered from when I did this job myself in August 2005.

I should straight away thank Hazen Arnold, Robert Goodwin and Fred May
Who offered quick and valuable input to me on this. Thanks also to Ian Read for previously posting the following procedure, which is relevant up to the stage of accessing and removing the wiper assembly.

For me, and despite a significant amount of information being
available, there were some critical comments or explanations missing. This might be just my own reading of the information but I ve added them here and I think they clarify the matter somewhat.

Blower Motor Removal and Installation
by Ian Read - Date: Mon, 26 Nov 2001

(AT - This procedure is followed to the point where the wiper assembly
can be removed. Clearly you can also get to your blower motor at the same time if you wish).

Here is the process that I followed since I could not find the
Instructions on the MB maintenance CD. Note all fastener lengths and locations, they are all different.

1. Remove the arm cover and hex screw from the wiper arm.

2. Remove the two rubber strips (AT - mouldings along the bottom edge
of windscreen) from each side of the lower windshield by pulling them
straight out.

3. Pull off the rubber weather-stripping that runs right across the
inner firewall area.

4. Remove the top outer left and right plastic covers (AT the
gutter units at each outer side of car below windscreen). Each are held in place in with two Philips head screws and are also joined to the top inner two covers with white plastic clips. Pull slowly to remove these fragile clips, ask me how I know. Remove the inner four Philips screws holding the inner top two covers down.

5. Remove the 4 screws holding the C shaped rubber grommet (AT and
it s black plastic retaining strip over), which is below the wiper arm

6. Pull off the engine side firewall weather-stripping. (AT don t
lose the spring clips under and inside the rubber stripping).

7. Just below the weather-stripping there are 4 plastic fasteners which
hold the sound insulation to the firewall, the inner two have a flower shape while the outer two are flat with two little holes. All four need to be loosened, the outer two will come right off. (AT I only found 3, 2 flower types centrally left and right and 1 flat one at right, ie. wiper motor side).

8. After step 7 you can pull the insulation forward slightly and find
two Phillips screws which hold the center plastic housing down. Remove
these two screws.

9. Remove the upper left and right inner plastic covers. (AT I think
this is the single little plastic grating over the pair of drainage ducts in the centre of car)

10. The center grate cover should now come straight out. (AT This bit
puzzled me at first. The central 2 vents are a SINGLE unit held by the
above screws as well as by the C-shaped metal piece on the grommet in 5 above)

11. The wiper assembly has four 10mm nuts holding it in place, two are
on the far right, and one each under the rotating center piece. Remove
these nuts carefully and make sure you don't drop them like I did as they can fall into the center black hole which is not accessible. (MIA one hex screw.) I found a similar one holding the A/C pipe on the left side of the inner firewall near the fuse-box which I used to replace the lost nut. (AT Before doing this, stuff some rags into the black holes. Also you will need to wriggle the assembly a fair bit to get it out. Take your time and it will shed the several years of grime).

12. Move the wiper assembly to the right. It is not necessary to
disconnect the power cable. (AT for preventative maintenance on the wiper unplug the cable from the motor and remove the whole assembly. Go to item 18).

13. Remove the outside temp sensor from the blower motor cover.

14. Pry loose with fingers the blower motor harness on the left of the

15. Unclip the 6-8 metal fasteners holding the blower motor cover down,
a couple may require a small screw driver, but be careful again. Remove
the cover.

16. Unplug the motor, and release the hold down strap using a pointed

17. Oil bearings with ATF. Check brushes.

As in Haynes (reassemble in reverse of above.)

Wiper Head Disassembly and Assembly (by AT)

18. Refer to MB procedure 82-0760 for removal and replacement of
wiper-to-motor linkage mechanism. This MUST come off to allow removal
of the wiper gear head cover. Hazen Arnold thinks you should scribe the crank location on the knurled axle. I agree because there is no squared end or similar locating device to ensure correct orientation on replacement.

19. Refer to MB procedure 82-0765 for removal and replacement of the
gear head. Note it must be in the 12 o clock position before it can be
removed. Take care of washers, C-clip and nut.

20. The above procedure is actually for removal of the large rubber
flashings (in 2 parts) from around the head assembly, but you don t
HAVE to either (1) remove them to get into the gear head, or (2) replace them unless weathered or damaged.

21. With gear head off, undo the FIVE small Philips head screws on the
underside and carefully separate the cover from the base and slide
mechanism. Take care with rubber gasket around edge.

James L Crofts has a useful photo story of this disassembly but implies
there are only 3 screws holding the gear head cover. But 2 are hidden,
hence item 18 above.

22. I cleaned all parts without further disassembly. Slides can be
re-greased with lithium or other long-lasting type. Connections between
oscillating arms, also bush for sliding wiper arm, (?felt) can receive
small amount of ATF or similar.

23. Re-assemble in reverse order.

Wiper Motor Disassembly and Assembly

24. Scribe the location of the crank on the motor drive axle before
undoing its nut. Axle is knurled and you could be 1 or more knurls off on re-assembly.

25. Remove the motor complete, undoing the 3 bolts on the alloy frame.
Remove plastic cover which clips over the unit.

26. I took the motor to an auto electrician for checking of brushes,
bushes etc. You might have the knowledge to do this yourself. Either way it should be done.

27. Re-assemble in reverse order. A bit of ATF, sparingly, on the
pivots of the motor-to-head mechanism is a good idea. Note the difference in ease of movement of the whole assembly.

28. Note: BEFORE re-attaching crank to motor drive shaft, take motor to
car and plug it in. Engage wiper switch once to ensure motor now stops at Park location. This is controlled within motor NOT the mechanism or the head.

Assembly in Car

29. Before re-assembly into the car, I cleaned up all round the base of
windscreen; areas hidden by the rubber stripping; inside air plenum,
around battery etc.; drains at corners of windscreen; gutters up sides of windscreen. Loads of debris accumulated all round.

30. When you have the wiper assembly mounted in the car operate it,
(best with blade raised) to check if the coverage is correct. If not, (refer item 18) at least it s easier to take out at this stage if you need to correct the orientation of linkage on the gear head.

31. Good dose of plastic treatment, (Meguir s makes one), to all rubber
and plastic parts is called for.


I took a lot of digital pictures right through the above work, mainly
for my own benefit so that I didn t have too many parts left over! However I would be pleased to pass this all on as a photo essay. Can it be posted in this form to the website or within FAQ s?

Any comment, correction or criticism should be directed to

Anthony Tugwell

13th August 2005


Virginia Beach VA

87 300SDL
95 E300D

Anonymous's picture
Re: Crazy windshield wiper

IRONHEART;202089 wrote:
Is it time to replace the Signal Indicator/Wiperswitch ???
Robert's information is all nice, but it does sound more like the wiper/turn signal stalk is faulty, as opposed to the contacts within the motor.

The correct diagnosis would be to disconnect the switch pins and see if it still happens; if yes then it's not the switch.

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