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Thread: Not selecting - Auto or Reverse. PLEASE HELP

  1. #11
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    Mar 2012
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    Burnley
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    You have to initially install the actuator correctly if you have had it off and then teach the computer where the bite and clear points are for the current physical actuator position.

    Nothing about the clutch is adjustable at all, just the actuator in and out positions can be learned by the gearbox computer.

  2. #12
    Join Date
    May 2011
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    Quote Originally Posted by Mjolinor View Post
    You have to initially install the actuator correctly if you have had it off and then teach the computer where the bite and clear points are for the current physical actuator position.

    Nothing about the clutch is adjustable at all, just the actuator in and out positions can be learned by the gearbox computer.
    Ah ok, I haven't had it off at all.

    I thought it could be adjusted without removing it completely? I'm not an expert on the matter, just learning as I go. But from my understanding so far, there is a rod which releases the clutch, and this can be moved closer without removing the whole unit? Am I along the right lines here?

  3. #13
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    No. The rod that operates the clutch arm that comes out of the actuator is automatically adjusted. It has the crappiest pair of rollers and a spring and works by praying to whatever particular god for another day of operation every time you use it. That should automatically adjust for normal wear.

  4. #14
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    Quote Originally Posted by Neo_the_One View Post
    Ah ok, I haven't had it off at all.

    I thought it could be adjusted without removing it completely? I'm not an expert on the matter, just learning as I go. But from my understanding so far, there is a rod which releases the clutch, and this can be moved closer without removing the whole unit? Am I along the right lines here?
    Right lines, wrong car.
    What you describe applies to the previous (450) model. Given Mjolinors woes with 451 transmissions, he knows how 451s work (or don't).

  5. #15
    Join Date
    May 2011
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    London
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    Thanks again for the replies.

    If I have to change the clutch, which I donít mind doing myself (as I like to learn new things), is this this a difficult procedure?

  6. #16
    Join Date
    Nov 2007
    Location
    BANCHORY
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    Diagnose correctly before changing components. Your problem can also be faulty clutch actuator. They are prone to failure due to ingress of water. Broken motor pinion is common.
    Drives a Smart Cdi - 65 to 85 MPG

  7. #17
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    Mar 2012
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    You should also diagnose the gear change motor unit after you diagnose the clutch unit and before you start ripping it to bits to replace stuff.

    There is little worse than a days work to end up in the same place.

  8. #18
    Join Date
    May 2011
    Location
    London
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    Thanks again for replying.

    My OBD2, gave me a P0805 - clutch position sensor circuit fault.

    and I took the car to Mercedes for a check, the guy said the actuator shoots the rod all the way out, and it requires a new clutch. And while changing the clutch should change the actuator with it.

    Said it would cost £2,200 Mercedes are a total rip off.

    Not sure if I should trust this opinion or not.

    What exactly would cause the clutch position sensor circuit to register a fault?

    I had the heater fan out recently as it stopped working, and struggled to get it passed all the wiring coming from the SAM unit, wondering if Iíve damaged the circuit in some way by doing that? The issue started shortly after.

    How can I test the actuator, and gear change motor?

  9. #19
    Join Date
    Mar 2012
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    Burnley
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    As the clutch actuator rotates a sensor in the actuator puts out pulses to the gearbox computer in exactly the same way as an ABS sensor does. A fault on this sensor does not mean you need a new clutch it just means that the ECU tells the actuator to rotate and expects a certain number of pulses back from the actuator, if keeps telling it to rotate until it gets that number. If it never gets to that number it will rotate for ever or at least until the ECU thinks it has been too long and registers a fault.

    I reckon you have a broken loom between the gearbox ECU under the passenger seat and the gearbox, well that is one option. You just have to go through it all until you find the fault.

    Is the car in London?

  10. #20
    Join Date
    May 2011
    Location
    London
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    Thanks - I do hope it’s something like that. It’s a lot simpler than a whole clutch replacement.

    Yes i’m in London.

    How can I go about testing this circuit?

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