ahost

I have a '03 C320. Recently my rainsensing wipers have become hyper-active! Once switched on, they will take a few swipes with pauses in between as intended, but after 2 or 3 swipes they will just continue to go continuously at full speed, even if there is just the slightest of mists, a single rain drop from time to time. They will even continue to go long time after I drive into a covered parking structure. I took the car to service, and they replaced the whole rain sensing module, but the problem persists. From time to time the rain sensor works as intended, but it's rare.

One guess as to the reason is that it could have something to do with the windshield rather than the rain sensing module. Maybe something with the surface tension? I noticed that on the area swept by the wipers the raindrops tend to run together (before using the wipers), whereas on the rest of the windshield they stay as distinct drops. Maybe that confuses the rain sensor? One slight confirmation of that theory is that yesterday I took the car to a wash a different place than usual, a drive through wash place that also applied wax (could change surface tension?), and today the rain sensor seems to work (it could still be a coincidence).

Have any of you had similar problems with the rain sensing wipers? Any solutions? In particular, if it has anything to do with the windshield, what can I do about it?

inFiniTE LooP

i've never had this problem, but one thing you could try to do is get some rain-X and apply it to the section you were speaking of where the raindrops end to run together. there is a foaming rain-x glass cleaner (comes with a free micro-fiber cloth for cleaning) that i used to use that would probably work well, it's worth a shot, and if it doesn't work, at least you've got some good glass cleaner and a free micro-fiber cloth to go along with it

MarkL

Yes, I had the problem many times, and I think you're right that the problem is with the windshield, or rather, how the water behaves in certain temperatures or humidity. Sometimes you'll notice that after a wipe, the water quickly dissipates, but other times, it spreads out but you can still see a layer -- this is when I had the problem. Also, if the blades wear a bit and you start having even slight streaks that pass through the area where the sensor is "watching", they won't delay and will keep wiping. It's not a perfect system but I still like it. (BTW, I've sold my C240 and I'm now driving something else [OK, BMW!]. I've only had it 2 months but so far, the rain sense wipers seem to be working fine.)

MB-BOB

The sensor works best with fresh wiper blades. The older the rubber gets, the less well it sweeps the water away, and the higher the sweep frequency. Rain-X helps too. But once your blades are changed at B-Service you'll notice a more normal function in the sweep frequency.

GGM

I use rainx and just had my wiper blades changed. Sweep frequency much improved.

GGM

elchinocache

i have the same problem but only in the winter. i think that the sensor on thw windshield gets covered by road crap and then it senses that its water so it keeps wiping like a mad man. i just take a napkin and clean the top of the sensor and that works for me.

rockintunes23

The same thing happened to me... stay away from rain-X for one, and I found over time... the wipers reset themselves and the problem is fixed. Since your car is getting old, I would take it to the dealership and have them inspect it. Time for a new CAR, wink wink. Over time, grandpa does not fix his own problems. You need to ditch him and get a new hot body in the drive way every once in a while.

Capt Nemo o2

Which rain-x are you refering to? the wipe on one or the one that replaces the windshield washer fluid? And why do you say stay away? What did you notice to say that. Personally, I used the rain-x washer fluid in my jeep and loved it, at 65+ mph, the wipers were not neccessary unless behind another car, which is pretty useful in a jeep since aerodynamics where not taken into account on the ZJ, and the wipers dont work at all when faster than 75mph

vadim

For me a squirt or two fixes the "strange" behavior of the rain-sensing wipers. The sensor does not seem to like dirty glass. Overall, I like them a lot.

inFiniTE LooP

i personally use the Rain-X washer fluid, and the Rain-X foaming glass cleaner and they work great! why rockintunes23 said to stay away from Rain-X is beyond me...

ahost

It seems there are divided oppinions about using Rain-X. Maybe there as an issue with Rain-X and the rain sensing function? If I try Rain-X and it seems to work badly with the rain sensor, can I remove it again? Or will it just disappear with time if I don't put on more?

Anyway, it seems many people have problems with the rain sensing. I'm amazed that MB just goes ahead and replaces the rain sensiog module, rather than advise first to try to do something about the windshield.

MarkL

Well, they're probably trying to keep people (you!) happy -- what would you have said if they told you to clean the windshield better, etc?? Plus, don't they get reimbursed and make some money by changing it out? When I used to take my car in they sometimes listed something on the repair ticket that needed repair (under warranty) and I highly doubted the need...

619er

Rain-X is supposed to leave an ultra-thin layer on your windshield that fills in all the microscopic pits and imperfections. It causes the water to run off faster BUT it also causes your wipers to create that irritating squeaky noise like they are wiping over dry clean glass (because the water has run off). This happened on my other car and I do not plan to use it on the windshield ever again. For the rear and side windows, it's fine. I had to wait till it actually wore off for the noise to disappear. Hope this helps in some way....

kompressor boy

personally, i hate the damn thing, its annoying as hell, i'd rather have more of my own settings than that dumb thing...came with the car, oh wells....yea, i got an 05 kompressor....thats one thing annoying about the car. heck, since im complaining...might as well say more :v the stoopid pull knob for fogs is a dumb idea too

have a good weekend guys :p

lars

My experience is that wipe on, polish off Rain-x leaves a thin, foggy film on the windshield. It's invisible most of the time but if the sun strikes it wrong there it is.

A cold weather problem with the rain sensors occurs in my area in the morning. If the car is parked outside overnight, for the first km or so of driving on these humid mornings the windshield is colder than the outside air, so it starts to fog over. The rain sensor definitely does not like this layer of mist and wipes continuously until the windshield temperature gets as warm as the outside air. But other than that it works fine.

For my part of the world, which gets many days of light rain each year, the rain sensor is probably the best value option MB offers.

Capt Nemo o2

That "stoopid pull knob" is actually a good design, it allows you to have just the fog lights on and not the headlights, which is much safer in extremely foggy conditions as the headlights (especially the BIX) reflect back to the driver.

TNblkc230wz

Rain - X, Don't leave home without it. It is one of the best safety devices in the rain. If your wipers are squeeking, it's not because of the Rain-X.

Also, I've never had an issue with my auto wipers other than the wipe once every time the car is started, wet or dry. I will ask the dealer about it at service B.

lars

Try turning the wipers off. That will solve your problem every time.