Rain Sensor

[MIW615]

Can someone please explain to me how the rain sensor on the windscreen works (W210). The reason for asking is that my wipers when selected on intermittent (first twist of the stalk) seem to have a mind of their own - keep going when the screen is dry the stop when it's raining. Funny thing is next day they may well work as they were designed to - are there any adjustments or is it just a poor idea / design?

 

[television]

In the little blue circle on the screen you have an LED at 45 degrees pointing at the circle, the pick up sensor is mounted the same way and picks up a good clean reflected signal from the circle. Should rain hit the circle it defuses the signal and the current flowing drops turning on the wiper, once dry again, the reflected signal is received in full and the wipers turn off till the next time water falls on to the circle

 

[MIW615]

In the little blue circle on the screen you have an LED at 45 degrees pointing at the circle, the pick up sensor is mounted the same way and picks up a good clean reflected signal from the circle. Should rain hit the circle it defuses the signal and the current flowing drops turning on the wiper, once dry again, the reflected signal is received in full and the wipers turn off till the next time water falls on to the circle

Malcolm, thanks for the detailed explanation, so could the fault be the sensor and if so do I assume this means a new windscreen - if so I'll live with it.

 

[MIW615]

Just had a thought - if a new screen is fitted is there an re-programming required by MB for the new screen / sensor?

 

[ennio]

I had a new screen fitted to mine by AutoGlass and they couldn't get the sensor to work - it had to to go to MB to be calibrated.

andrew

 

[MIW615]

I had a new screen fitted to mine by AutoGlass and they couldn't get the sensor to work - it had to to go to MB to be calibrated.

andrew

andrew - was the re-calibration covered by the insurance?

Maybe mine just needs re-calibrating - any views on this?

 

[ennio]

Yes, or by AutoGlass - certainly not by me

First AutoGlass fitted the screen under insurance (plus £50 from me): the rain sensor didn't work. AutoGlass ordered a new rain-sensor from MB and fitted it themselves; still didn't work. Next time I went to MB I asked them to investigate the problem; I passed the report, along with the cost of the report, on to AutoGlass who then agreed to pick-up the bill for the re-calibration too.

In the end it cost AutoGlass more than it might because they were ignorant about the need for re-calibration and fitted a probably unnecessary new unit.

 

[television]

The best guy is away on holiday that can answer this.

Replacement screens cause more problems than enough and they have to be exact.

It will not be your screen at fault MIW, I will try and find some more details

 

[Blobcat]

I used to get occasional issues on my W210 when the screen was greasy. A good clean with the screen polish and it was fine again.

 

[MIW615]

It will not be your screen at fault MIW, I will try and find some more details

Thanks Malcolm - did you manage to find out more details.

Is there seperate controls that can be checked on MB computer?

 

[hampshire jock]

I have a 2003 ml 270 cdi 'inspiration' spec. does anyone know if i have rain sensor wipers ? is there something i can specifically look at to see if this is fitted to my car ?

thanks in advance

 

[television]

Morning Jock, yes, just turn to position 1, if they give one sweep and stop then you have got them,if the carry on at slow speed then you have not got them

 

[hampshire jock]

thanks - i dont then

 

[angus falconer]

Malcolm, thanks for the detailed explanation, so could the fault be the sensor and if so do I assume this means a new windscreen - if so I'll live with it.

Mine occasionally goes nuts when either (a) there's smeary early morning condensation on the screen for the first quarter of a mile or so (b) it's exceptionally hot and sunny

I just switch the wipers off for a few minutes - usualy does the trick

 

[whitenemesis]

Malcolm, thanks for the detailed explanation, so could the fault be the sensor and if so do I assume this means a new windscreen - if so I'll live with it.

If the sensor is faulty it's a quick 10min job to replace, no need to change the screen. The new sensor must be adapted to the screen. This is a job for STAR.

There is a small possiblity that you may have bubbles in the screen around the bonding for the sensor lenses. This is a documented fault in WIS and your MB dealer will know what to look for. If this is the case then, unfortunately its a new screen Possibly under warranty

 

[whitenemesis]

Morning Jock, yes, just turn to position 1, if they give one sweep and stop then you have got them,if the carry on at slow speed then you have not got them

The newer auto wipers will not give the automatic single wipe on ignition switch on (mine doesn't). Try switching to 1 if they wipe and keep wiping then no auto wipers (assuming it's not raining!!) If they don't move at all (or give the single wipe then stop) try spraying the area of the screen around the RVM (outside obviously) with a plant mister or similar. The wipers should come to life.

 

[whitenemesis]

Can someone please explain to me how the rain sensor on the windscreen works (W210). The reason for asking is that my wipers when selected on intermittent (first twist of the stalk) seem to have a mind of their own - keep going when the screen is dry the stop when it's raining. Funny thing is next day they may well work as they were designed to - are there any adjustments or is it just a poor idea / design?

As Malcolm has explained the system works on infrared reflectance. The later sensors have many more lenses (8 in fact) arranged in a grid patern around the central light sensor for the headlamps. I think but am not 100% certain the roadsters retain the single lens as described by Malcolm. The sensor must be adapted to the screen via STAR and through STAR the sensitivity can be adjusted. The area of the sensor should be kept clean as road film can send the wipers into overdrive!

 

[television]

As Malcolm has explained the system works on infrared reflectance. The later sensors have many more lenses (8 in fact) arranged in a grid patern around the central light sensor for the headlamps. I think but am not 100% certain the roadsters retain the single lens as described by Malcolm. The sensor must be adapted to the screen via STAR and through STAR the sensitivity can be adjusted. The area of the sensor should be kept clean as road film can send the wipers into overdrive!

Thank you young man, I knew that you would know, there are limits as to how much one can absorb and how much new technology one can read about

 

[whitenemesis]

Thank you young man, I knew that you would know, there are limits as to how much one can absorb and how much new technology one can read about

That's exactly why we have these forums!

 

[television]

That's exactly why we have these forums!

At least you make a clean sweep with your post