Setting up Front Windscreen wiper

[Mikimogo]

Hi,
I have got to replace my front windscreen wiper motor on my Yr 2000 C220 CDI but believe that it has to be set up after. I would appreciate it if anyone could advise me how this is done.

 

[Dec]

This... http://members.lycos.nl/mbenz/windshield_wiper.htm will give you an idea on how to access the wiper mechanism. Why do you think you need to replace the motor, what symptoms do you have?

Dec

 

[Mikimogo]

Hi Dec,
Thanks for the reply, My front wiper stopped in the

upright position yesterday and after inspection the nylon cog

or worm in the motor has teeth broken off thanks to the metal

cog it conncts to, the motor still goes but there is no drive

to the wiper just a grinding noise so as you cannot just get

the cog to replace it's a replacement motor job. MB want

£206+vat for a motor so I've got one via 1st Choice Spares on

the internet for £65+vat+postage. I have read that on

replacement it needs setting up properly,

 

[Dec]

First park the motor, yes I know your blade parks in the center of the screen but it is the motor you need to park, to park the motor turn on the wipers at the stalk to normal speed then turn off at the stalk, when the motor stops it is parked. Remove keys from ignition.

Next disconnect the power from the motor (I think it is a 5 pin plug and socket) remove the motor and mechanism together in one piece, there are 3 bolts on the mechanism, undo these first, then there is 1 awkward bolt going through the bulkhead which should be undone about 4 or 5 turns but not removed completely if you are lucky there may be a white clip on this bolt (windscreen side) which can be undone easily.

The motor is detached from the mechanism via 3 bolts and 1 ball joint which can be levered off (grease this ball joint when you are refitting)

The bottom left picture in my link, which shows the motor and mechanism for a left hand drive car however as you look at your assembly the arm that is on the motor should be aligned exactly with a V mark or similar mark on the body of the mechanism.

To make sure that the replacement motor is in its correct park position before you fit to the mechanism you could plug the replacement motor into the socket and get someone to switch the wipers on and off again at the stalk, it will now be in its correct park position. Remove keys from ignition. KEEP YOUR FINGERS WELL AWAY FROM THE MOTER ARM WHEN YOU DO THIS.

When you have fitted the new motor to the mechanism via the 3 bolts and ball joint the motors arm (about 3 inches long) should be aligned exactly to the V mark and the long lever (about 12inches long) should be in line with the 3 inch long motors arm and the wiper blade, if it were fitted should be in its correct park position.

If the blade is not in its correct park position, then the nut directly under the RED arrow in picture will need to be undone about 5 or 6 turns but not removed and the blade moved to its correct position, the bolt is then retightened.


Dec

 

[Mikimogo]

Hi Dec,
Thanks for the detailed explanation it's just what I needed your a Gent. My wiper arm parks in the horizontal position it just packed in in the vertical position. The new motor should be here tomorrow so hopefully I should be able to get it sorted with your instructions.

 

[Aussie Nick]

Unclipping the plastic shroud around the middle of the windscreen may cause you some problems. It is common for some of the clips to break. When you remove the shroud push the wiper to the normal horizontal parked position (If you can't get it there using Dec's method) The motor is not going to be used anyway. Suggest you take a close up photo of the assembly for reassembly purposes. The reassembly can be difficult to get the right W movement . The diecast markers mentioned by Dec are all important but the photo of the assembled unit is insurance against confusion which can easily occur onthis job.
Heed Dec's warning iT IS EASY TO CAUSE INJURY TO FINGERS ON THIS JOB INCLUDING UNCLIPPING THE PLASTIC SHROUD

 

[Dec]

Here is a few pictures, the will speak a thousand words.

Dec

 

[Mikimogo]

Hi all,
Thanks for all your help, I studied all the points an took photos as I went along on the dismantling and it went fine it was all done in about 40 minutes I couldn't believe it. It seems to be working fine but I didn't see anything that caused it to jam in the first place si I'll keep my fingers crossed. Once again thanks! Your advice and photos were invaluable.

 

[Dec]

It must have been either, the blade was frozen to the screen when the wiper was turned on or the guide rods under the “turtle shell” cover had dried out due to lack of lubrication, A lack of lubrication (with greese) puts a strain on 4 weak points in the assembly, the are as follows;

A. Nut 1 that locks the wiper arm in the correct park position on the windscreen.
B. Nut 2 at the motor which lines up the motor arm to the V mark. (motor must have been parked first before adjustments are made)
C. The coged wheel and worm drive inside the motor gearbox.
D. The coged wheel, which cant be seen until the guide/hub section is removed (via nut 1) this can slip on its shaft, it is solely responsible for the in/out action of the wiper blade, the symptoms of its failure are that the tip of the wiper blade doesn’t retract and so strikes one or both sides of the windscreen trim, otherwise the sweep of the blade is normal. see attached picture E.
Also persistently running the wiper on a dry windscreen will also put a strain on all of the above points.

Lubrication of the guide rods under the “turtle shell” will help prevent any of the 4 weak points from causing a breakdown of the mechanism. That’s why lubricating 3 or 4 times a year is so important, it only takes 5 minutes.

If you still have the old motor I would love to see a close up picture of the sheared teeth and the inside of the motor cover as there is some kind of “points” in there.

Dec

 

[Mikimogo]

Hi Dec,
Right, I will get those guide rails greased as I didn't have the turtle shell cover off. It could well have been that was the problem because it couldn't have been frozen as it wasn't that cold and the wipers had been on workingfine for half an hour when it happened, it was halfway through its travel in the straight up position when it just stopped without any warning. I will take a couple of photo's and post them tomorrow (if I can find out how) There isn't a tooth left on the big nylon cog that goes to the metal worm but you will be able to see all the bits of nylon.

 

[Mikimogo]

Hi Dec,
Sorry about the delay with the pics but I will attempt to attach some to this post!

 

[Dec]

Thanks Michael, the were well trashed, useful to see what state the can get in.

I have just discovered something I didn’t know and wasn’t aware of concerning the existence of alignment marks on the back of the assembly casing.

I am attaching 2 revised picture of pictures, A and C in post number 7.
Sometimes I think I know it all, then I realize I only know the halve of it, you learn something new every day.

Dec

 

[Mikimogo]

Hi Dec,
Yes I agree it's one big learning curve. I've just checked on my photo and there doesn't seem to be the lining mark on the case unless it's under that black strip but all the mechanism seems to be in the same place as your photo and I didn't move any of the wiper arm mechanism so hopefully it's okay they seem to be working and parking okay.

 

[Aussie Nick]

Dec The timing marks are very hard to see when the assembly is exposed .They are there and it is hard to reassemble the thing without reference to these almost invisible marks.

 

[Dec]

Right Michael, the are under the black stripe all right, glad to see you got it sorted o.k.

I agree Nick, If you know the are there, you will find them, I was not aware of there existence when I worked on mine, took a couple of goes reinstalling it, to get it parked in the right position.

Dec

 

[Darren Oldfield]

Hi Dec

I know this is an old thread, but very useful for others like me who have the same wiper problems as Michael. My wiper also stops halfway through on the return sweep, so I was on the point of ordering a replacement motor (my motor's nylon wheel showed signs of wear, although it's not nearly as trashed as shown in Michael's photos), when I realised the gearing may be the source of the problem. All component parts are well greased, so I doubt it's a friction issue. My head tells me that if the motor is knackered the wiper wouldn't move at all, so I now have doubts about my initial diagnosis, therefore can you suggest a sure-fire way to check whether the cogged wheel slips on its shaft? That's the only thing I can think of - if I can't definitively i.d. the problem I'll opt for replacing the whole motor/gear mechanism, just in case. I've already held the stripped mechanism while it's operating (lots of care required to ensure fingers remain attached to my hand!), but I can't really see any shaft-slipping.

Many thanks
Darren

 

[Dec]

Hi Darren
A sure-fire way to check whether the clogged wheel (I’m referring to the one in the cut-away picture) is slipping on its shaft, is that, it will, sometimes or all the time, strike the windscreen side trim on one or both sides of the screen. If this is not happening then it is o.k.

As you have lubricated the mechanism under the “turtle shell” cove, there are only two other likely possibilities.

1…Nut 1 or Nut 2 are slipping and need to be slackened off, reseated and retighten, ensuring the alignment marks mentioned in pictures are correct.
2… The more likely reason why the blade stops in mid sweep is that the motor nylon gear is indeed trashed by the worm drive, you can’t see all the teeth on the nylon gear when you remove the motor gearbox cover. See post#17

I would suggest you run the wipers to recreate the fault, until the blade stick in the mid-sweep position then immediately turn off the wipers BY REMOVING THE KEYS FROM THE IGNITION, not at the stalk, his will leave any damage on the nylon gear facing the worm drive, if you then remove the motor gearbox cover I think you will find significant damage to that part of the nylon gear.

It is important to note that the worm drive’s contact with the nylon gear is what drives all of the mechanism and the blade across the screen, so you can imagine the stress at this point of contact if for example, the blade was frozen to the windscreen, if the nylon gear couldn’t move (because the blade is frozen to glass) the worm will just chew up the nylon gears, but only at that point of contact. This chewed up part would correspond to where your blade is stopping on the windscreen.

Hopefully your problem is number1 above, but if it is number 2 then you will need a replacement motor, scrap yard is best bet, most MB dealers won’t sell the motor on its own , without the mechanism, your existing mechanism is probably o.k.

Strictly speaking your motor is not knackered, if it is running, but it is a component (nylon gear) of the motor that is knackered.

Let us know how you get on, or if you need any further clarification.

Dec
Edit; “I've already held the stripped mechanism while it's operating (lots of care required to ensure fingers remain attached to my hand!), but I can't really see any shaft-slipping.” It would not be possible to see anything while the motor is running, only when you dismantle the mechanism.

 

[Darren Oldfield]

Dec
Many thanks for the advice. Been away for several weeks but will try your suggestion asap.
Darren

 

[Darren Oldfield]

Hi again Dec

I couldn't understand why my nylon cog had very little damage, yet the motor still showed the same common symptoms as knackered cogs (i.e. stopping in upright position, etc etc). After a couple of re-runs I finally noticed that one of the metal edges / ridges on the worm screw had sheared off (caused by metal fatigue or misalignment perhaps), and this point was bang in the centre of the cog in the stopped position. Therefore I'm guessing the broken edge probably can't fit into the cog's grooves during its turn and so it probably slips or stops the entire worm movement. Very frustrated that I'll have to get a replacement motor for 1 damaged worm screw, but it's looks like I'll have to, especially as I'd be worried about any unseen damage caused to the cog by a sharp broken metal edge. Many thanks for your help along the way.

Cheers
Darren

 

[Dec]

Hi Darren

As you say, it must have been metal fatigue, you would expect the much softer “nylon” to fail rather than the ridges on the metal worm.

Dec