Sometime my automatic wipers don't start as expected, so I have to intervene manually.
Is there a way to adjust/calibrate the rainsensor to make it more sensibel ?

 

AFAIK - No, there isn't. However others may know something I don't but in three years on this forum, I've never seen anyone mention recalibrating the auto-wipers. I too, get the problem you have, so it annoys me too, but one can always use the manual settings.

 

How does the sensor work?

 

Yeh ... I find on mine that it's a bit slow to get going when the rain starts if the screen is dry and I usually have to pull the stalk for a 'one-wipe'; after that it works fine. Personally I don't find it a bother

I think it's just a general characteristic of the system; I don't think there's any adjustment.

 

I found the rain sensing on my X308, 2 XK8's and now my current XK to be too sensitive.

It drags the wipers over a barely wet screen which can cause scratching if the screen is already dirty. Consequently I have them in manual mode.

Graham

 

The rain sensor is an optical transducer that is sensitive to changes in infra-red light penetration of the windshield created by the refractive effects of water droplets.

Graham

 

Likewise, mine in auto mode often want to go into high speed when an intermittent speed will suffice. I only use auto when it's a light mist or road splash and they will stop at lights, etc.

Also have the issue where they won't quite start on their own, but a "one wipe" will get them going as well.

My Cadillac had a "sensitivity" knob for the auto wipers. Miss that.

 

I'm with GGG. I'd like to find someone who can figure out if there is a way to wire a resistor in or something to cut the sensitivity by a third to a half.

All Auto seems to do is try to wear out wipers.

 

I find auto useless. It has a mind of its own only slightly relevant to what is really needed.

 

I found the wipers in the X350 to be far too sensitive but my '07 XKR is pretty much spot on.

Some people have had success taking the sensor off the X350, cleaning off the goop that is used to stick it on then reattaching it with less goop:

Erratic auto-wipe function: a story with a happy ending!

 

I removed my rain sensor and cleaned off the silicone, today the auto wipers worked perfectly for the first time ever!

 

where was that silicone located ?
I only know silicone to be on top of the windscreen due to wipers..

 

The silicone is used to glue the sensor onto the glass hence it is between the sensor and light (or IR) falling on the sensor.

If the silicone is too thick or has degraded this can affect the sensitvity of the sensor.

Silicone is normally used as a sealant but can be used as a glue but you may have to tape the item in place until it sets.

I have used it recently when I painted the E tag (toll road sensor) black and glued it to the back of the rear view mirror where it is now invisible and the windscreen is clear.

The advantage of silicone is that it can be peeled away if you have to remove it and doesn't leave a mess.

 

Yes I have exactly the same issue, although I don't really consider it to be an issue!

 

Sounds worth trying; so how did you fix the sensor back onto the screen please ?

Dave in Glos.

 

It's secured with a metal clip against the screen. My best guess is that the silicone is there just to provide a clearer optical connection between the sensor and the water drops on the outside.

Unfortunately, either the silicone degrades over time, or the sensor is just too sensitive from the get-go on these cars and this has the effect of dulling its response. I don't know if the auto wipers actually worked properly on a brand new car or not... I would assume they did and the silicone is what degraded resulting in false signals to the sensor (i.e. bubbles and fog in the silicone make the sensor think the window is wet when it isn't).