help. wipers gone crazy!

I have a problem with wiper blades going off by themselves. The car is 98 slk230. Basically, if you turn them on, they won’t turn off. I went to dealer fordiagnostics, and they claim that the combination control lmodule is faulty and want $900 to replace it. Did anyone come across this problem? I am just wondering if there is another way around this problem.

Thanks.

Hi,
They may be right but my own experience suggests that the control modules are often taken as the first item to change, when somebody doesn't know what to do, rather than the last.
What codes did the dealer discover when they interogated the OBD? Exact wording please or are they just guessing. No code would support my premis.
I don't have the wire diagram with me at the moment and I am going away for a few days but how about unplugging, inspecting and refitting the wiring plugs to the wiper and the combination control units. If this doesn't work try the wiper switch for good measure but of course this is in a dry zone.
When you unplug them look VERY carefully (magnifying glass) for any signs of water or TRACES of corrosion around the connector pins and sockets and if so endeavour to remove any deposits with contact cleaner or similar.
Control units often malfunction because poor interwire insulation, corrosion at plugs etc allow voltages to get from a main supply lead across to a low current signal wire. I've always maintained that power and signal leads should be separated but this has implications which cost. Remember the jumbo that exploded TWA 800?
I don't suppose this problem started after rain or a car wash etc did it? Let me know how you get on. If problem persists I look up the circuit when i return.
S

Thanks for the info. The started periodicaly, now always.

quote:

unplugging, inspecting and refitting the wiring plugs to the wiper and the combination control units. If this doesn't work try the wiper switch for good measure but of course this is in a dry zone.

I am not familiar with wiring in slk at all, as all of my previous cars were jap cars. Where is it located? Is there an online help /diagrams?

thanks.

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Tried that, still no good. Is there anyway I can disconnect the wiper motor? I tried pulling the fuse, but the roof will not work with that fuse out. This thing is just driving me mad.

i don't advise you to disable the wiper for it concerns safety when driving on the rain... therefore i cannot give the info.

life is more important than the $900 to fix it.

have it fixed please.

Hi, Just back from holiday.
Read your reply and you added a bit of information. Was intermittent. now constant.
The wiper motor has a switch in it that detects the correct position for the wipers to PARK. This switch/contact supplies power to the motor independent of the column switch. The contacts on these switches can "get dirty" (arc etc) and can therefore stick together causing the wipers to continue running even with power off.
Not sure if the motor is designed to allow any form of maintenance without looking.
Not sure how technical you are so suggest dealer like Sleepwalker but don't allow them to rip you off for a control unit when you need a wiper motor or just a switch/adjust.
Let us know how you get on.
Stuart

quote:

The contacts on these switches can "get dirty" (arc etc) and can therefore stick together causing the wipers to continue running even with power off.

Where are the contacts located? Should I look for the wiper motor and the contacts with it. Your suggestion is more reasonable that the dealers, because I think if the module would go out, the problem would have been constant. However, like I said it started by not shutting off a few times a week, and now it is on if you switch it on and will stay on. If I put the position 1 on the stitch, the wipers would stop after 10 revolutions, and most of the time it would be in the middle of the window( they would not return to original off position).

Shak,
I don't have a wiper motor in front of me to examine.

However the contacts will be on, or in, the wiper motor somewhere.

First step will be to move the wiper motor from the vehicle and to have a look. Removal is quite straightforward from under the bonnet in the area immediately in front of the screen. Ensure you disconnect the battery since wiper motors are very powerful and due to the non switched power supply can potentially start at any time. (This in fact is the nature of your problem)

Four wires (wrapped as one) run from the wiper motor N6/1 directly to the N10/3 combination control unit. There is no plug and socket connection at the wiper motor.

However, it is possible that these wiper motors are sealed and designed in such a way that you cannot take them apart unless of course you know better.

Good luck.

Stuart

Thanks a lot. I now have a weekend project.

Hey there. I have taken the wiper motor out and inspected the connectors, the 4 wires going from control module to wiper motor.

quote:

The wiper motor has a switch in it that detects the correct position for the wipers to PARK. This switch/contact supplies power to the motor independent of the column switch. The contacts on these switches can "get dirty" (arc etc) and can therefore stick together causing the wipers to continue running even with power off.

Are the contacts the 4 wires? The wires are connected to the bottom of the wiper motor with some sort of glue-gun looking substance. I opened the bottor metal cover and inspedted the wires. There were 3 resistors connected there and i cleaned some grease that got there. Unfortunately, the problem is still there.

Now, do I need to take the actual motor cone out too? I think that thing just has the mechanical gears and stuff.

Without the component in front of me I really can't help much more. You need to trace where the four wires go. OK there are some resistors. (surprise No.1) but there should be some form of switch which can sense the position of the output spindle, not the motor shaft which will rotate many times per sweep of the screen.

If there is no such device to sense position then MB must sense position using current waveform which will all be in software in the control unit in which case I guess you are back to the original diagnosis from the dealer, the control unit.

If indeed the sensing is done by software it is still possible that the wiper motor itself is on the way out and giving a completly incorrect waveform for the control module to analyse. I repeat that control modules (except in very early life) don't usually go wrong unless the car has been jump started incorrectly etc.

No need to take the motor itself apart since this is working. There will be wires connecting to the motor rotor through brushes however.

When you put it back together make sure the unit is watertight. The gung you refer to will likely be a silicon RTV sealant like you use around the bath tub to make the access point for the wires watertight.

Let us know what happens since this may help others. Stuart

Still here. A quick question, what ius the Mercedes part # for combination control module? Is it n 10-3? I am trying to find a used one. I cant see myself giving them $800 for a stupid module.

Thaks.

bump.

Hey there. I called the dealer today to get the part number and they wont give it out. He claims it is their policy. Did anyone heard this crap from any other dealer. This one is located in Jax fl, Brumos motors.

Is there a online catalog I can use to locate the part #.

http://www.mercedesshopen.com/Shop/Index.php?Language=LangEng

Try here for a 2nd hand part and price.

Bazzle

A170 820 09 26

Thank You.