Rear wiper on when starting the car

Jul 31, 2020 | 10:46 PM

Hugo Duguay

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Joined: Sep 2018

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Mercedes GLK 350 2011, Porsche 911 Carrera 4S

Rear wiper on when starting the car

Hi guys,

I own a 2011 GLK350 I bought new in 11'
Never had any problem of any sort since then.

Today I opened the trunk to put stuff in, I up in the car and start it. Nice sunny day.
Still on "Park" I realized the rear wiper was working.
I went to stop it using the switch only to realise it was already off but the wiper wouldnt stop.

I decided to active the switch manually, wiper will continue to work and when I put the switch to off position it will stop in the middle of the window.
I gave another try , wiper stopped at another location and the third time it stopped almost at the correct position but not exactly where it should be.

Does that ring a bell?
Any idea where I can start investigating?
I tried to research this problem on the forum but it doesnt seems to be common.
I have to add I washed the car 2 days ago...

Thanks for your help.
Hugo

Last edited by Hugo Duguay; Jul 31, 2020 at 10:51 PM.

Aug 1, 2020 | 05:33 PM

Hugo Duguay

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Joined: Sep 2018

Posts: 5

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Mercedes GLK 350 2011, Porsche 911 Carrera 4S

Just a little more info I also tried other rear wiper switch positions. Both position to spray windshield wascher fluid gives the same results.
the wiper works for about 5 cycles then stop anywhere in the window.

If I leave the wiper to the on position it will work for 5 cycles, stop anywhere for 5 seconds and start again only to stop at a random position.
I found it funny that the car work perfectly in the morning and this trouble shows up in the afternoon during a sunny day..

Aug 2, 2020 | 12:36 PM

ZZGlk

Member

Joined: Aug 2015

Posts: 113

Likes: 25

From: Washington State

2013 GLK 350 4Matic

Sounds like the wiper motor switch is intermittent. Most wiper motors have a limit switch that indicates when the wiper is in the "home" or at rest position. If this switch or the contacts on it is intermittent or flaky, then the motor will start up, trying to return to the at rest position. It may also run for a few cycles and then stop when it thinks its back in the home position. Usually, the switch is a cam on the end of the motor asembly that makes contact with the brushes and tells the motor when to run and stop. The switch can get flaky over time by building up carbon from the brushes arcing. Cleaning up the switch contacts and removing the carbon can fix the problem. I haven't had that problem on my GLK but you should be able to remove the cover on the inside of the hatch and access the wiper motor and switch.

Aug 3, 2020 | 04:10 AM

Hugo Duguay

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Newbie

Joined: Sep 2018

Posts: 5

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Mercedes GLK 350 2011, Porsche 911 Carrera 4S

Hi thanks for your reply!

Okay that's exactly my tought and Im about to dismantle the rear deck and see if I can clean the motor board.

I did a little test and removed the front 7.5amp fuse used for rear wiper control.
The rear wiper still was triggered when putting the ingnition to the ON position.
So Im now sure the activation switch is not the culprit.

I activated the rear wiper and removed the key when it was reaching almost the rest position and I removed the 15amp rear fuse so it wont move anymore.
This is just to be sure it doesnt act up each time I start the car and scratch the window for nothing.

I will have some time to work on the car in a few days and clean-up the motor. I will then put the fuse back and hope for best.
Ill let you know how it goes.

thanks again
Hugo