How do rain sensitive wipers work

[996jimbo]

I have rain sensitive wipers on my '98 C43. They have always been a bit iffy and I've had them adjusted a number of times, but still seem to be inconsistent. I once had them adjusted correctly but then promptly got a cracked windscreen - with the new windscreen fitted they were back to being inconsistent.

Anyway, my question is this:

Does the sensor on the windscreen control the frequency of wipes (does it make the logic decisions and switch the wiper on / off) or does it 'merely' relay to some other control unit the amount of rain for the other unit to make the decision? I'm pondering getting a new windscreen unit.

Thanks.

 

[eric242340]

I have rain sensitive wipers on my '98 C43. They have always been a bit iffy and I've had them adjusted a number of times, but still seem to be inconsistent. I once had them adjusted correctly but then promptly got a cracked windscreen - with the new windscreen fitted they were back to being inconsistent.

Anyway, my question is this:

Does the sensor on the windscreen control the frequency of wipes (does it make the logic decisions and switch the wiper on / off) or does it 'merely' relay to some other control unit the amount of rain for the other unit to make the decision? I'm pondering getting a new windscreen unit.

Thanks.

I think the probability of a duff windscreen is very high. The sensor only sends a signal to the control module. the sensor is just that a sensor. Bit like your sense of taste, you taste it and your tongue is the sensor, it then relays signals to the brain, (in this case the receiver is the module)

 

[eric242340]

I should add to this. The rain sensor is located at the top centre of the windshield. We have so many cases of fake winshields it frightens me. But im in Asia and thats life here. However in UK, you should not have this problem. What markings do you have on the new screen? Pilkintons,MB?

 

[television]

I think the probability of a duff windscreen is very high. The sensor only sends a signal to the control module. the sensor is just that a sensor. Bit like your sense of taste, you taste it and your tongue is the sensor, it then relays signals to the brain, (in this case the receiver is the module)

Sorry eric its nothing at all like that.

In the module on the inside of the screen there is a Light emitting diode (LED) and a receiver. The LED sends up a beam onto the sensor at 45 degrees,the receiver picks up this reflected signal. Should any rain fall on to the little reflective circle on the screen then the beam is defused and this then turns on the wiper.
Problems could be when the module on the screen is re fitted, it the old adhesive is not removed the module could be too far from the screen to focus correctly, or the point of focus is not on the reflective circle in the glass.

 

[eric242340]

Sorry eric its nothing at all like that.

In the module on the inside of the screen there is a Light emitting diode (LED) and a receiver. The LED sends up a beam onto the sensor at 45 degrees,the receiver picks up this reflected signal. Should any rain fall on to the little reflective circle on the screen then the beam is defused and this then turns on the wiper.
Problems could be when the module on the screen is re fitted, it the old adhesive is not removed the module could be too far from the screen to focus correctly, or the point of focus is not on the reflective circle in the glass.

Old cars sigh

 

[996jimbo]

I should add that I'm just on my third windscreen.

So, Television, if the thing is not working correctly it might be worth removing, cleaning up the surface and re- fixing?

And how is it recalibrated? Or is it recalibrated - when it goes to MB what do they do to adjust the sensitivity? I have the plastic outer cover off mine at the mo and am wondering about having a poke around in the unit, or if there's anything to poke.

Thanks for the response so far by the way.

 

[996jimbo]

Old cars sigh

P*ss off!

 

[eric242340]

P*ss off!

Nothing personal please.

 

[television]

I should add that I'm just on my third windscreen.

So, Television, if the thing is not working correctly it might be worth removing, cleaning up the surface and re- fixing?

And how is it recalibrated? Or is it recalibrated - when it goes to MB what do they do to adjust the sensitivity? I have the plastic outer cover off mine at the mo and am wondering about having a poke around in the unit, or if there's anything to poke.

Thanks for the response so far by the way.

I do not think that there is any form of calibration for these, but I will check over the week end. where it is fixed is critical as is the distance from the screen

 

[television]

Been thinking and if there is any form of calibrating it should be in the unit on the screen, ie Gain,focus etc

 

[Blobcat]

Simple fix with mine is to wash and polish the screen with Autoglym screen cleaner and polish.

 

[996jimbo]

Simple fix with mine is to wash and polish the screen with Autoglym screen cleaner and polish.

Tried that over and over again.

But the good news is that after I fiddled with the plug a little and tapped the unit a couple of times it has suddenly started working properly over the full range from no wipe to constant.

Hurrah!

 

[television]

Tried that over and over again.

But the good news is that after I fiddled with the plug a little and tapped the unit a couple of times it has suddenly started working properly over the full range from no wipe to constant.

Hurrah!

Then a bad soldered connection is possible after being removed a couple of times, that would make more sense

 

[television]

Light dirt on these things does not cause a real problem, when a water bubble sits on the spot this deflects the beam.