Blocking protection problem front wipers
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Thread: Blocking protection problem front wipers

  1. #1
    LEGACY VENDOR
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    August 15th, 2006
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    Blocking protection problem front wipers

    I’ve been having a problem with my front windscreen wipers just stopping for no apparent reason while they’re switched on (I don’t mean the ‘intermittent’ function – this is in both normal and fast ‘continuous’ modes).

    Having read the workshop manual I know that the wiper mechanism has a ‘blocking protection’ function which cuts the power to the wipers if they’re switched on and there’s no wiper park signal received by the Body Control Unit for a period of 16 seconds (e.g. if the wipers are frozen to the windscreen or something physically obstructs them from moving). The BCU then only turns the power back on again after waiting 3 minutes or if the ignition is turned off & on again – and sure enough that’s exactly what mine do, although neither waiting for 3 minutes or keying off the ignition is much of an option at 70mph on the third lane of a motorway while passing a truck that’s throwing up huge quantities of spray.

    Although I always believe that an ECU is the very last thing that should be blamed for a fault I thought I’d better first check that it wasn’t sat in a puddle of water or something due to a leak. I removed the passenger seat to inspect the BCU and its connections and everything looked absolutely fine.


    Body control unit lives under passenger seat


    BCU

    I used my Faultmate to check for DTCs for the Body Control Unit and sure enough it had stored “Wiper motor blocked, park switch or wiper relay defective”. The wiper relay only costs 5 so I thought I’d try that first




    Wiper relay is mounted next to transfer box ECU behind the battery
    2003 4.4l V8 Range Rover Vogue

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  3. #2
    LEGACY VENDOR
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    Re: Blocking protection problem front wipers

    but when I phoned to order one I was told by the Land Rover dealer that theyd never sold one before the clear implication being that it was unlikely to be the relay at fault. I therefore decided to buy a new wiper motor/linkage assembly instead.

    Ive now fitted it and - guess what - the problem is still there . I took the old motor apart to examine the park switch and theres nothing obviously wrong with it


    Cam on motor drive gear which activates park switch


    Wiper park switch

    Ive therefore now ordered a wiper relay and am waiting for it to arrive. In the meantime Ill have to keep my fingers crossed that this is going to fix the problem.

    I just wondered if anyone else had had a similar experience with their front wipers?

    Phil
    2003 4.4l V8 Range Rover Vogue

  4. #3
    JUNIOR ROVER LEBoyd's Avatar
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    Re: Blocking protection problem front wipers

    Quote Originally Posted by RRPhil View Post
    but when I phoned to order one I was told by the Land Rover dealer that they’d never sold one before – the clear implication being that it was unlikely to be the relay at fault.
    Maybe the reason they hadn't sold any is because people buy them from BMW or somewhere else not realizing that the LR dealer's price isn't that bad? I just did a quick check for the part and there are several places that sell them - although I think it's interesting that they are not English (I did see German on ebay). Generally, relay failures aren't really unheard off (i've had relay failures on my Tahoes more than once), so I'm surprised about the "surprise" of the dealer.

    Just some thoughts I had about this. Anyway, i hope the relay works for you.
    2004 L322, 265/50R20 Yokohama tires. "Mrs. Jones" ("We've got a thing going on")

  5. #4
    LEGACY VENDOR
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    Re: Blocking protection problem front wipers

    I'm pleased to report that it was the wiper relay causing the problem - and it cost just 6 to replace it



    Just a shame that Id already spent 127, unnecessarily, on a new wiper assembly before getting to this point!

    Phil
    2003 4.4l V8 Range Rover Vogue

  6. #5
    FRESHMAN ROVER
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    Re: Blocking protection problem front wipers

    well done phil
    a thread with a conclusion , some threads start of well but never get an ending
    2000 p38 4.6 v8 30th aniversary prins sequential multi point lpg
    1990 3.5 v8 defender 90
    2004 4.4 v8 l322 vogue prins sequential multi point lpg

  7. #6
    SOPHOMORE ROVER medcapequip's Avatar
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    Re: Blocking protection problem front wipers

    Nice insight and story. Anyone know if the relay would cause the wipers to stay in the up position?
    2003 Range Rover HSE
    Los Angeles, CA

  8. #7
    Premium Member
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    Re: Blocking protection problem front wipers

    I'm actually really surprised that you believed the dealer and went against your gut on this one. Most of us (yourself included) try to actually diagnose the problem and not just throw parts at it until we get lucky... you did that here but second guessed yourself. Glad it worked out in the end but it sucks you blew 127 to remind yourself that you're smarter than the average dealer parts changer.

    Quote Originally Posted by RRPhil View Post
    I'm pleased to report that it was the wiper relay causing the problem - and it cost just 6 to replace it



    Just a shame that I’d already spent 127, unnecessarily, on a new wiper assembly before getting to this point!

    Phil
    05' MKIII-
    Wanted: D90
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  9. #8
    NEWBIE
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    Re: Blocking protection problem front wipers

    Does anyone know where this relay is on a 2009 5 litre petrol model please?

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