Rain sensors
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Joined: Sep 2014
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W203 C320
Rain sensors
I've got a 2001 C320 and it's equipped with the optional rain sensors, I would just like to know what a failed sensor would do? On my control stalk the 1st setting is supposed to be the 'rain sensing' mode and 'II and III' are independent of rain intensity.
From reading previous threads, I gather that if the sensor fails, the wipers will revert to intermittent mode (wiping infrequently and regardless of whether there is rain or not?) when the control is placed in the 1st setting. My sensors do seem to be a bit sluggish recently, I was driving at city speeds and a rather large amount of water had to build up on my screen to trigger a wipe but on other occasions it's wiped even a small amount of water away. Can this component degenerate over time or is it a 'it's broken or it isn't' case?
From reading previous threads, I gather that if the sensor fails, the wipers will revert to intermittent mode (wiping infrequently and regardless of whether there is rain or not?) when the control is placed in the 1st setting. My sensors do seem to be a bit sluggish recently, I was driving at city speeds and a rather large amount of water had to build up on my screen to trigger a wipe but on other occasions it's wiped even a small amount of water away. Can this component degenerate over time or is it a 'it's broken or it isn't' case?
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Joined: Jun 2008
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Some sensors are glued on & some embedded. If glued they can become inconsistent. Clean the area in front of the sensor to remove even a trace of silicone or mineral deposit. The rain sensing can be recalibrated with a Star.
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Joined: Jul 2011
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From: Hawaii
2017 GLA 250, 2011 C63 P31 (p30 w/ lsd) (in repair), 2005 C230 Sport Eurocharged, 2003 C320~sold
Will have to look in Star to recalibrate mine as they are inconsistent when they wipe as well. Sometimes I just kick it to the low speed and back to intermittent then it seems better. 
Thread Starter
Junior Member
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W203 C320
My ones just seem to have really de-sensitised to low rainfall. It can certainly tell the difference between an absolute downpour and a light rain but when it's a shower or drizzle, it has no idea when to wipe.
