R129 - Window wiper gets stuck

[LeaUK]

Ok - on to the next new problem....

Anyone experienced stuck wipers? Intermittent used to just get stuck occasionally, then kick start itself again and operate correctly, however now intermittent just fails.

Symptoms are that the blade just stops in the most odd positions across the window, and for each wipe will stop in a different position. Often intermittent just stops altogether.

Also, the blade fails to find the park position - and I think this is my clue. I have to time the use of the wiper switch just right!

There are two 'modules' that control the wiper blade N10/2 (which sits in the black box above the fuse box) and the K26 relay module, located just below the blade somewhere.

My suspicion is that the park sensor in the motor assembly is failing such that the module 'thinks' the blade is parked when in fact it isn't OR that the relay driving the motor (K26) has carbon'ed contacts.

Has anyone else resolved this before?

Cheers
Lea

[elau]

Love to help, but I don't drive mine in the rain so I don't even know if the wiper works

Put plenty of RainX on the windshield and you don't have to worry about the wiper. I do that to my daily driver, the 300E.

[jjrodger]

There are a few threads about servicing and overhauling the wiper system (not specific to the R129) in the Tech Help forum. I think MBenzNL was the main contributor to it. This is a link to his description of the wiper mechanism on his C250 on his website (I can't imagine the fundamentals are any different).

http://members.lycos.nl/mbenz/windshield_wiper.htm

[LeaUK]

Thanks JJ - I scanned all the forums but couldn't find that much - cheers 'eagle eyes'....


Lea

[LeaUK]

Managed to get some time last week to strip down the wiper parked sensor (slip rings) attached to the wiper motor. Unfortunately this unit looks typically 'Mercedes clean', however I bent the slip ring contacts such that they press down firmer on the ring, cleaned them and re-greased the whole unit.

Now the wiper has only failed once over a period of four days (in the rain) - but guess that means something still isn't quite right!

The K26 relay module is located adjacent to the ECU box and isn't too difficult to remove. To inspect the relays within, the RTV seal needs breaking - contacts on mine all look excellent!

Thought this may help someone else

[Kebowers]

The sl-600 (94 129) I have has a speed sensitive system when in low or intermitent positions. It stops the wiper when the car is stopped. If your also has this speed sensor, it may be causing the erratic action.

[LeaUK]

Mine is also speed sensitive, but it doesn't stop the intermittent wipe it just reduces the time interval from 5 seconds to 8, under 10mph.

This speed sensitivity is controlled by the K10/2 module (adjacent to the fuse box) and I have no reason to suspect it's failing - however thanks for the tip.

My wipers (at their worst) failed to wipe correctly operate on intermittent (or park) virtually every wipe, so now failing only every four days is much improvement

[stevecora46]

Sounds like the wiper relay. Mine had exact same symtoms. Replaced the relay, problem solved.

i have seen the control relay cause this same problem on a few 129 models
Ray
mercedessd@cox.net

[LeaUK]

Interesting as this is the next item I will investigate. It's a sealed unit, but only by RTV so it's easy to prize open. I've already had a brief look (there are around 7 relays inside!) and so maybe the contacts of one of the relays are sticking or have carboned..

Time for more investigation........

[LeaUK]

Update:

Yes, it's the K26 relay module. Stripped it down to reveal 4 relays. Cleaned all contacts using P800 'wett and dry' and reflowed all components on the pcb.

Haven't had a problem in two days - now bearing in mind that the wipers failed every wipe before the clean this looks promising ;-)

I'll post a few pictures of the module shortly for the benifit of others.

Thanks for the pointers.

Lea

[LeaUK]

Two weeks later and still fine....resolved

[LeaUK]

After the forum HDD crash I'd thought I'd make a repost of the pictures I added last week.

Hope they're useful to someone

The first picture is from a LHD vehicle, the next is my RHD car.

[Pete Geither]

Thanks, and very interesting. Like a lot here, I hardly ever see rain in the SL. but when I have had to run the wipers, they do odd things. Mostly they want to park on the right side in the middle of the intermediate sweep. So that module is under the cowl cover ?

[LeaUK]

If they are indeed parking in weird places I would seriously suspect the K26 - that's exactly the symptoms of mine..

It's under the cover on the drivers side.