W202 Wiper stopping in middle of screen

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If the wiper arm can be moved by hand then as you say there is either a nut/s loose or something else is broken or the nylon gear/worm drive inside the wiper motor gearbox is damaged/striped of some teeth.

The running all the time problem could be one of the Yellow relays being faulty or the wiper stalk is causing the fault somehow, perhaps not in the twisting part of the switch but further down where it enters the steering wheel.

A wiper motor, that has no faults, when turned to 0 will switched off automatically and come to a stop when it has finished its cycle, it doesn’t know where the wiper arm is on the screen, the fact that the wiper arm didn’t park correctly is solely down to a loose nut on the mechanism which has knocked the wiper arm out of sync with the motor.

Dec
 
Thanks again Dec.

As you write " wiper motor, that has no faults, when turned to 0 will switch off automatically and come to a stop when it has finished its cycle". I was assuming the motor has not switched off because it has not finished its cycle. The original problem occurred when the wiper was switched on and working and suddenly stopped in mid stroke. It was not trying to park at the time.

What interests me is that the wiper moves freely by hand back and forth from centre screen to the passenger side of the screen but when I try to move it manually in the other direction from centre of the screen to the correct park position on the drivers side of the screen it is quite firm and does not move by hand. Do you think this is significant?
 
Some times the wiper blade stops because of a loose nut, you automatically assume the motor has also stoped but the motor may just keep going until it switched off, a wiper motor that is disconnected from the mechanism makes very little noise, it’s the motion of the wiper blade on the screen and wiper mechanism that makes 90% of the noise that you hear when the wiper is working, the motor when running free is fairly quiet.

Are you absolutely sure the motor really is running all the time when wiper switch is at 0, the motor really is very, very quiet if it is running free and not connected to the mechanism. You wouldn’t be able to hear it inside the car, you would need to open the bonnet with the engine OFF to hear properly.


What you describe below is indicative of a loose nut, when you pull the arm one way its “undoing” the nut and when you pull the arm the other way you are tightening the nut.

“ What interests me is that the wiper moves freely by hand back and forth from centre screen to the passenger side of the screen but when I try to move it manually in the other direction from centre of the screen to the correct park position on the drivers side of the screen it is quite firm and does not move by hand. Do you think this is significant?”

Dec
 
100% sure the motor is running all the time whatever position 0-3 the stalk switch is set. Relays are ok. Motor sounds very loud when ignition on and engine off.

Suspect motor is drawing current all the time either because it is not parked and therefore power when in 0 is continuing to go to and be drawn from the park terminal inside the motor, or the motor is damaged causing it to draw current all the time.
 
100% sure the motor is running all the time whatever position 0-3 the stalk switch is set. Relays are ok. Motor sounds very loud when ignition on and engine off.

Suspect motor is drawing current all the time either because it is not parked and therefore power when in 0 is continuing to go to and be drawn from the park terminal inside the motor, or the motor is damaged causing it to draw current all the time.

Less speed more haste! I did not really explain what I meant very well in the above paragraphs. Ignore them I will start again below!

100% sure the motor is running all the time whatever position 0-3 the stalk switch is set. Relays are ok. Made no difference when relays were changed for new ones. Motor sounds very loud when ignition on and engine off.


Normally when the circuits in the motor casing for running the motor are switched off by putting the stalk switch into position 0 a different circuit is activated inside the motor casing for the purpose of parking the motor. This internal circuit in the motor goes to the same place but via an internal switch in the motor. Whilst on the switch allows the motor to continue running. The internal switch is turned off automatically when the motor reaches the park position. If this internal switch is broken so it is on all the time or other damage inside the motor is causing the switch to be by passed the motor will run all the time.
 
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There are 2 circular tracks, the inner, which has a brake in it, when Switch 1 reaches it the motor will stop i.e. it will park.
Switch 2 is live all the time when ignition is on, perhaps one of the switches is damaged/twisted.
Note, inside your motor will look different to the one below.
The wiper mechanism in the video will be opposite to yours as the car in video is LHD

Dec

[YOUTUBE HD]7ca6h6HRskU[/YOUTUBE HD]

10132d1206645781-w202-wiper-problem-motor.jpg

10133d1206645826-w202-wiper-problem-worm.jpg
 
Thanks for all your advice Dec.

Problem found. Job done.

The motor was running all the time whatever position 0-3 the stalk switch is set. Relays for normal running and intermittent are ok. Made no difference when relays were changed for new ones. Motor sounded very loud when ignition on and engine off.

Normally when the circuits in the motor casing for running the motor are switched off by putting the stalk switch into position 0 a different circuit is activated inside the motor casing for the purpose of parking the motor. This internal circuit in the motor goes to the same place but via an internal switch in the motor. Whilst on the switch allows the motor to continue running. The internal switch is turned off automatically when the motor reaches the park position. If this internal switch is broken so it is on all the time or other damage inside the motor is causing the switch to be by passed the motor will run all the time.

A new motor was therefore ordered yesterday and came this afternoon. The new motor ran quietly and perfectly unconnected with ignition on and stalk switch in on position. In the off position the motor parked itself and turned off. This proved the fault was in the motor. Transmission gearing was therefore removed, old motor taken off it and new motor put on in its place. The nut holding the old motor and the nut for adjusting the parking were both tight and the parking was correctly aligned to the marks. There was no damage to the transmission gearing which is good as a new one is £600 compared with a motor price of only £300! The gearing looked like new. The gearing was nicely greased but the rod which comes out of the gearing and moves up and down as the wiper goes across the windscreen and is attached to the wiper arm although nice and shiny when viewed whilst it was fully extended in the centre of the windscreen had no grease visible externally. I temporarily put some bearing grease on it and I will tomorrow buy a silicon spray, remove the small cover and squirt the spray around that part of the mechanism. The wipers run smoothly and quietly and operate correctly at all speeds, and park correctly when turned off.

I have nowstripped down the old motor and it has a stripped plastic main gear. The portion of the gear that is stripped was that which is in contact with the worm when the wiper is on the passenger side of the screen. Hence free movement in that arc - the worm and gear are not engaged so the wiper was free to move. The portion of the gear that was in contact with the worm when the wiper is on the drivers side of the screen is still intact, so when I moved the wiper towards that side of the screen the gear jams with the stationary worm and motor.

Thanks again for the great photos.
 
Good result and thanks for the fed back.

De
 
I see this is old but thought I'd add my experience. I'm in Australia and my 1998 W202 C280 wiper stopped. Took to the dealer where I have it serviced. Was quoted $5,200 for new wiper motor and assembly. They charged me $418 to tell me that. I've got a working motor and assembly from a wreckers and will attempt the swap myself.
 
Hi Dec hope you get this message..
I replaced my front wiper motor on my W reg w202 estate after it gave up the ghost (shredded teeth) it worked all fine and dandy.. driving in heavy rain the wiper started to judder at the top point and slow down but towards thw bottom and back up it worked fine. Now the wiper sits at 1 oclock as you look from inside, the wiper works on every speed but always stops at 1. Ive looked at your previous posts and checked everything lines up, it didnt so l followed your instructions, plugged it all back in turn on the ignition and bang straight back to 1 oclock.!!!! Help MOT due and it in my direct line of vision....
 
If you haven’t already done so, lubricate the wiper mechanism as in video below, Lithium or any grease will do. Lack of lubrication may have caused the damage to the teeth in the first place.


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First, you need to park the WIPER MOTOR before you remove it from the car;

Turn the wiper on for a couple of sweeps of the wet windscreen then turn off the wiper stalk switch to off position = 0, wait 2 seconds for the blade to come to a stop at its incorrect position at 1 o'clock on the screen then remove keys from ignition.

The WIPER MOTOR is now parked; your wiper blade is not parking where it should be, so, you are now going to remedy this by realigning the alignment marks for nut 1 and or nut 2.


a-jpg.9718



Refer to the above picture; if the V mark is aligned with the short motor arm then it is correct.

Next, slacken off nut 1 and realign the alignment marks with the park position marker, left Red arrow.

When you are finished, the back of the mechanism should look like above picture with both sets of alignment marks set as illustrated, MAKE SURE both nut 1 & 2 are tight.

Refit and test, its quite difficult to get the wiper blade to sit exactly where it should be at the bottom of windscreen, if you get it close, then it will do till after your MOT.


Dec

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