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intermittent rain sensor

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by jberks, Nov 21, 2012.

  1. jberks

    jberks Senior Member

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    Your Mercedes:
    Jaguar XF 3.0 S, LR Freelander 2, Fiat 500 & Fiat Panda
    I've had an occasional fault since the car was new and never resolved it, but it has started to be more frequent (4 times this morning) so I really need to sort it now.

    I switch on the rain sensor, all works normally for a few minutes and then it stops working. At this point if I press the single wipe button or push further for wash/wipe, nothing. It's dead. Turning the knob either off or onto normal wipe and straight back and all is well again for a bit. Used to be ok for a few weeks but clearly whatever the problem is, is now getting worse.
    Has anyone seen / resolved this issue?
    I'm wondering whether it's the switch but as its a complex thing, I'm not sure what would cause this.
    Any ideas?
     
  2. whitenemesis

    whitenemesis Senior Member

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  3. OP
    jberks

    jberks Senior Member

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    Not had them read yet tbh - but I've reproted the fault a couple of times over the years and they've never found anything.
     
  4. Dec

    Dec Senior Member

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    Is the internals of your wiper switch similar to the one in attached picture?

    Dec
     

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  5. OP
    jberks

    jberks Senior Member

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    Haven't had it apart but the exterior is the same.
     
  6. Dec

    Dec Senior Member

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    If the one sweep push/squirt isn’t working when the intermittent fault occurred then it could be wear on the PCB track, perhaps the contacts have worn the PCB track away, resulting in poor contact and rotating the switch cures the fault for a while.

    If you could bend… ever so slightly… both contacts so as the both rests on a fresh, unworn part of the PCB then it might cure the fault.

    All conjecture of course, it could be something else entirely.

    Dec
     

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  7. OP
    jberks

    jberks Senior Member

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    Thanks DEC. Great pics and very helpful.
    To be honest, in my experience, when the PCB is worn, it's a losing battle. You may breathe some life back into it for a bit but it rarely lasts.
    I guess if it's fed via the selected mode, then from your pics, a switch fault could explain the problem. After all, it spends 99% of the time set to use the sensor (I rarely switch it off) so it could have worn it's way through the pcb, knocking out the single wipe and wash functions in the process. It would certainly explain why moving the handle gets it working again. Hard to know without strupping it down and testing the circuits though. That said, perhaps teh next time it fails, I'll just move the knob a small amount back and forth and see what that does.
    Euromerc appears to have a replacement for £40 so it could be a worthwhile punt...
     
  8. Dec

    Dec Senior Member

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    Try some switch cleaner too, just in case there is some tarnish or the like involved and causing a bad contact.

    Dec
     

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