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Speedo sensor / instrument cluster problem.

Discussion in 'A3/S3 Forum (8L Chassis)' started by TwinCamMan, Nov 6, 2013.

  1. TwinCamMan
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    TwinCamMan Member

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    [Nov 6, 2013]
    I had the instrument cluster out of the car and a few days after the speedo stopped working. Removed the cluster again and ensured that all connections were good but still no joy. Scanned the car for errors and only got the oil level sensor fault that I've had for a few months now, but nothing for the speedo. Swapped over a speedo sensor that was sitting in an S3 box out the back of a friends house for the last few years, still nothing. Plugged in the VCDS again and ran an output test for the instruments and all working, the speedo and rev counter go through the motions as they should be.

    Correct me if I'm wrong but if the output test is fine everything from the ECU to the instrument cluster is good. And if there is a fault at the speedo sensor (including wiring) it would show up on a scan. What am I missing here?
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  3. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Nov 6, 2013]
    Unplug the sensor and see if you get a fault code?

    It might just be the type of sensor it is doesnt give you any codes when faulty?
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  4. TwinCamMan
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    TwinCamMan Member

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    [Nov 6, 2013]
    Good thinking, I'll check that out and get back to you.
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  5. @udi A3
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    @udi A3 Site Sponsor Site Sponsor VCDS Map User

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    [Nov 6, 2013]
    Are the cam type levers intact on the plugs? they should pull the plug tight and snap shut. I went to a car recently where both were broken and that was causing his intermittent issues. As the problem happened after removing dash that could be likely. Also maybe a bent or dislodged pin.
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  6. TwinCamMan
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    TwinCamMan Member

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    [Nov 6, 2013]
    Everything is connected properly in the instrument cluster, cams working and cliping in ok and pins are all straight. Surely the output test wouldn't have worked if it wasn't connected properly, would it? This problem isn't intermittent, speedo doesn't move at all.
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  7. @udi A3
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    @udi A3 Site Sponsor Site Sponsor VCDS Map User

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    [Nov 7, 2013]
    Output test just activate the dials through the obd. It doesn't test the input signal to dash
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  8. TwinCamMan
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    TwinCamMan Member

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    [Nov 7, 2013]
    Unplugged the sensor and it made no difference. Still no fault codes. Surely if the clocks weren't connected properly the output test wouldn't work?
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  9. @udi A3
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    @udi A3 Site Sponsor Site Sponsor VCDS Map User

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    [Nov 7, 2013]
    output test is just that, it activates the clocks outputs.
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  10. rouHe
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    rouHe New Member

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    [Nov 7, 2013]
    Had almost the same thing. First speedo went dead and then gas meter was popping around. Seems that speedo meters motor in the dashboard is dead + in my case also the "processor" is "dead". Waiting in line for a repair :E
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  11. RobinJI
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    RobinJI Member

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    [Nov 7, 2013]
    The fuel gauge will jump around if the speedo isn't receiving a signal. I believe the fuel gauge is 'smoothed' when you're driving so it's actually readable, but to make it jump straight to the correct reading when you turn the key it shows a direct, unsmoothed reading until you start moving. As the speedo signal's the only way it knows if you're moving, if the speedo's not connected it'll jump around as the fuel sloshes around in the tank. If this is happening, in my eyes this suggests it's the signal that's missing, rather than an issue with the clocks.

    (PS, I'm speaking from experience having driven my car with and without the diff-speed sensor connected, the fuel gauge is all over the place without it connected, but sits steady with it plugged in.)
    #10

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