Hi

With the rain recently, I have been trying to fix my rain sensor. With a sensor plugged in, the wipers do not wipe intermittantly, instead they wipe at the same speed as setting 2. The car does this with 2 different sensors of the same model, so I doubt both sensors are faulty. I do have the blue glass bit that came stuck on the windshield, so I am puzzled to whats wrong.

With the sensor removed, I get intermittant wiping at one swipe every 5 seconds or so.

Can anyone think what is wrong with the wiper system?
I asked the stealership over the phone and they gave me a variety of answers, including saying that there may be a can-bus error? or that the setting is not set in star diagnosis. The car is a 2001 c240, and according to a vin decoder, it did come with a rain sensor, so unless the previous owner disabled the rain sensor, the rain sensor should be working.

any help/input is appreciated.

 

Hmmm, that's interesting. I'm not sure what the problem is -- I have a problem with my rain sensor too (or at least I think it's a problem). I keep it on the rain sensor mode (1 switch over), and when I turn off the car and turn it back on, it wipes once (although there is no rain). I don't know whether this is the standard or what, but the BMW remains on rain sensor and doesn't do that when you turn off and on the car.



Tee_Tz.

 

Where is the rain sensor? Is it the round black thing on the hood near the hood vents?

 

the rain sensor is in front of the rear view mirror, inside a black plastic shell... with my car, the light sensor is seperate (2001) but in newer cars the sensors are intergrated into one. The rain sensor is a black rectagle cube like thing that snaps onto a blue piece of glass attached onto the windshield

 

check the windshield and make sure it's not chipped, scratched or dirty where the sensor meets it. Sometimes on the outside there might be a small piece of debris or dirt and might trigger it to wipe.

Hope this helps!!!

 

It wipes once to alert you it's on, rain or shine.

 

I do believe it is the MB standard. My 02 does the exact same thing.

 

mine, with the sensor plugged in, just sweeps and sweeps and sweeps. I just cleaned the glass and sensor... no change.. any other ideas?

 

Clean -- and I mean thoroughly clean -- the windshield above the sensor. You might be amazed...

 

The rain sensor consists of four infrared leds and four photo sensors. If the windshield is dry the light from the leds is reflected back to the photo sensors. This is interpeted by the front CAN, and it leaves the wipers off. If there is a droplet of water on the sensor it bends the light beam and allows it to escape. Since the beam is not reflected the CAN turns on the wiper. Anything on the windshield that can bend infrared light will run the wipers. Car polish, waxes, and Rain-X can absorb or bend the light and cause undesired operation of the wipers.

MB-Bob is right, clean the windshield well, use Bon Ami or your favorite cleaner to get everything off the glass.

If the LED's are burned out, the wipers will run. You can't see the light with the naked eye, but many video cameras, and a lot of digital still cameras can see the light from the windshield. See if they are on by pointing a camera at them at night.

 

there is also the slight possibility the previous owner has it disabled in the car with star diagnose. If the windsheild was replaced with the incorrect model (blue glass vs. green glass) and the overhead control panel was not programmed accordingly, it may do the same as well. The rain sensor's 3 pin plug goes directly into the overhead control panel that houses the sunroof controls. The control panel has a few programmable strings regarding the rain sensor in it.

 

Mine does the same thing, i think its just the saved setting from the last turn on, takes a whipe to make sure none accumilated during its off period. That is a benz mech told me.