Mercedes-Benz Forum banner

1 - 20 of 21 Posts

Registered
Joined
201 Posts
Discussion Starter #1
Hi,

My rain sensor works, but performance isn't crash hot. Sometimes there is so much rain on the screen that I have to switch the wiper to position II or III. Other times, the wipers aren't needed but come on anyway - sometimes constantly until I switch it to 0.

I believe that in facelift vehicles, the rain sensor was changed from a unit with 4 sensors to one with 10 sensors. Was this due to poor performance of the first generation rain sensors installed on pre-facelift cars?

I've also noticed that occasionally when on position II, the wipers actually stop for a period before restarting. Shouldn't they be constantly on (at the slower speed) in position II?

Any advice would be appreciated.
 

W220 Moderator
Joined
5,655 Posts
Hi,

MB use 2 different types of Rain Sensor, one is called Kostal, not sure what the other one is now...................

Don't know if this applies to W220, but if it does, and the vehicle has had either Sensor or SAM replaced and incorrectly coded / not bothered coding it, then it could cause a problem.

Also if the car has had a replacement screen, and they've fitted the wrong screen it could cause issues !!

Try getting it looked at on SDS, but you'll need someone who really knows what they are doing ...................

Mels C Class had an incorrectly coded Rain Sensor, took me ages to suss it out, and even then it was only because I just tried the other coding option in desperation, and lo and behold it worked correctly !!

HTH,

Cheers Dave
 

Registered
Joined
2,400 Posts
SDS -STAR Diagnostic System

This is the dealer-level computerized diagnostic/programming system covering all recent Mercedes Benz vehicles.

Many independent garages (indies) have either the official system ($$$$$) or a Chinese clone of the system ($$$).

Any owner who is willing and able to do moderate DIY repairs, maintenance and testing should very seriously consider purchasing a clone system. You can buy a turnkey system for perhaps $600, or buy the major parts and put a system together for perhaps $450. The system can be readily sold after the need goes away, recovering most (or all) of the cost.

There are hundreds of posts about such systems online, with this forum being one of the better sources of info.
 

Registered
Joined
201 Posts
Discussion Starter #5
Thanks for the fast reply Dave.

The screen was replaced in the past year or so, but the correct screen was used (the screen guy actually asked us in advance whether the rain sensor had 4 or 10 sensor segments). With the old screen the rain sensor didn't work at all. It's still possible it's not coded correctly though.

I also had another look, and it appears the wiper blade may sweep a little too low for the rain sensor area to be completely wiped - but if the wiper blade was any longer, I think it would be off the edge of the screen in the home position...

What were Mel's C class wipers doing before you changed the coding?

I still don't get why in position II the wipers stop sometimes though.
 

W220 Moderator
Joined
5,655 Posts
C Class Rain Sensing worked as and when it felt like it.

Regarding wipers stopping in II , that's another reason to get it on SDS, you can see what is going on via SAM Unit, and OCP too regarding Rain Sense issues.

Don't forget that the Blade on Passenger Side is the one that sweeps the Rain Sensor, so with the Cantilever Arm it may not go off Screen Edge ;)
 

Registered
Joined
201 Posts
Discussion Starter #7
Thanks Dave. I guess wipers would get a work out in your part of the world :)

As first course of action I will try a longer wiper blade.

Will let you know outcome.
 

W220 Moderator
Joined
5,655 Posts
2 things spring to mind here,

Firstly, does your car have the "Cantilever" Wiper Arm on the Passenger Side ?

Secondly, are the Wiper Blades 28" Long ?

When my Wipers wipe the Screen, the Passenger one goes well over the Rain Sensor, at the top of it's sweep it is around 1" - 1.5" from the Top of the Screen !!
 

Registered
Joined
201 Posts
Discussion Starter #9
Dave,

The wiper blades are 26" long.

The exact wipers used are these ones: TRICO FORCE | TRICO庐

When in the home position, the end of the passenger wiper blade is around 1" from the side edge of the windscreen.
 

Registered
Joined
201 Posts
Discussion Starter #11
Thanks Dave,

For clarity, is both the driver and passenger side meant to have 28", or is it driver side 26" and passenger side 28"?
 

Registered
Joined
201 Posts
Discussion Starter #14
Fitted 28" wipers, but the rain sensor still isn't working well..

With the longer wipers, the outermost inch or so of the passenger (left) side doesn't make full, flush contact with the glass (this is right where the rain sensor is), due to the blade being so far away from the wiper arm. Is this always the case? We're using good quality wipers here - full price is $45 each ($90 for a pair!). We waited until they were on sale...

Does anyone know if Benz moved from a 4-segment to 10-segment rain sensor on later models due to problems with the earlier rain sensors?
 

Registered
Joined
201 Posts
Discussion Starter #15
Hi again,

Possibly two separate problems, but I have observed the following:

- On all wiper speed settings (auto, slow, and fast), the wipers sometimes just stop sweeping. Switching to 0 and then back on again causes the wipers to start sweeping again. This fault happens intermittently and relatively infrequently.
- Wipers have started not to "home" correctly before stopping, when the wipers are switched off. In some cases, wipers are an inch or two above the proper home position.
As a result, sometimes the wipers sweep once (when the car is turned on the next time), presumably because the car knows the wipers aren't resting in the home position.

Any advice? Obviously I want to avoid a situation where the wipers completely fail, if possible.
 

Registered
Joined
406 Posts
What does SDS say? In my case, the (f) shows the problem to be the motor.

Stopping wiping in the middle of their motion suggests a problem with the motor. My understanding is that the sensor only affects the intermittent setting, which is really "wipe when needed". On low or high, they should just keep wiping.

I suspect you're in need of a motor...about $215 from MBOEMParts.com...
 

Registered
Joined
201 Posts
Discussion Starter #17
Hi Astro14,

I don't have easy access to SDS. But to be clear, when they do stop when still switched on (to the II or III setting), they return to home position before stopping.

It's when they're switched to 0 during wiping they they often park an inch or two out of position.
 

Registered
Joined
406 Posts
Hi Astro14,

I don't have easy access to SDS. But to be clear, when they do stop when still switched on (to the II or III setting), they return to home position before stopping.

It's when they're switched to 0 during wiping they they often park an inch or two out of position.
I think parking an inch or so out of position is normal, isn't it? They're "ready" to wipe again when the sensor says so.

I wouldn't worry to much about that...

But, help me understand here, when they're in position II or III, they keep wiping until YOU select them off, right?

Because in II or III, if they stopped and weren't selected off, then I would suspect that the motor is at fault, or is being overloaded by the transmission.

I've not tried to grease/lubricate the transmission, but I'm certain that there are articles available on how to do it. I would use a white lithium grease. The transmission itself is crazy expensive, like, $1,000 when I saw it once...so, I would sure try to clean/lubricate it before I swapped in a new one...
 

W220 Moderator
Joined
5,655 Posts
Hi Astro14,

I don't have easy access to SDS. But to be clear, when they do stop when still switched on (to the II or III setting), they return to home position before stopping.

It's when they're switched to 0 during wiping they they often park an inch or two out of position.
Hi,

C' mon now :devil,

You've been a good W220 owner / member on here long enough to have realised that you really should spend the 'wonga' on your own SDS System, and teach yourself how to use it, with some help from "us lot" if needed :wink

I know I keep 'banging on' about SDS, but it is not just a Diagnostic Machine ................

It is a complete System, an arsenal of Workshop Manuals & Info, Parts Catalogues etc etc, it has all the same Software that MB Main Stealers do, SDS does absolutely everything that the Dealers can do ............... and more (because Developer Mode is not enabled on MB Dealers machines), they are not allowed to use it, it is for Factory use only, but we get it enabled on a clone system ;)

I can never stress enough, with these Cars it is as essential as Screwdrivers, Torx Bits and Spanners ;)

HTH
 

Registered
Joined
201 Posts
Discussion Starter #20
Yeah, fair point Dave, I will talk to Dad about getting one as he would get more use out of it than me, actually. How much are they going for these days? Any recommendations on which one to get?

As for the wipers, yes, even on II or III they stop sometimes.

And they are definitely meant to always park in the home position (especially if they are switched off). My rain sensor doesn't actually work very well, so I rarely use the first setting.
 
1 - 20 of 21 Posts
Top