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magnetic pick-up/speed sensor

Discussion in 'Excavators' started by jey_c, Apr 21, 2011.

  1. jey_c

    jey_c Senior Member

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    What current flows to TVC solenoids on komatsu dash 6 excavator, if the speed sensor is defective and the working mode is H, should it be a constant current like when using G mode? Thanks
     
  2. John C.

    John C. Senior Member

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    The current through the TVC is measured in milliamps and generally isn't something you need to do. The manual will give you an ohm reading range which has always worked for me.

    Usually when the speed sensor quits working the computer dials you back to about 50% of pump absorption torque. You can shift the prolux switch which if I remember right would give somewhere around 65 - 70 percent.

    How do you know the speed sensor is bad?
     
  3. jey_c

    jey_c Senior Member

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    Well John, it is easy to teel that the speed sensor is bad, all you have to do is to measure its resistance while engine is stopped, and also you can measure voltage generated from it while engine is rotating
     
  4. Chris5500

    Chris5500 Well-Known Member

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    What's the underlying issue here and which speed sensor are you refering to?

    It's a dash 6 machine, if there's a problem there will be a fault code.
     
  5. jey_c

    jey_c Senior Member

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    The speed sensor is well known, it is mounted on the flywheel housing.
    Actually there is a fault code, that' why i am asking about the consequence on hydraulic speed.
     
  6. Chris5500

    Chris5500 Well-Known Member

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    It can vary, usually jerky operation or stall the engine etc.

    What's the fault code?
     
    Last edited: Apr 22, 2011
  7. jey_c

    jey_c Senior Member

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    It is a E227
     
  8. John C.

    John C. Senior Member

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    jey_c
    I was just asking to make sure I didn't steer you down the wrong path for troubleshooting your machine. I hope you didn't take offense with my question.

    Here is an observation I've seen with the Komatsu speed sensor issue. When the speed sensors over heat and burn out from the bell housing being full of oil, the computer doesn't put out a fault code. I figured it was because the sensor is shorted through and the computer would sense a voltage on the ground side. What I have found was when there was a fault code, there was an issue with the wiring harness.

    Good Luck!
     
  9. jey_c

    jey_c Senior Member

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    John my friend, i really appreciate the way we do here for troubleshooting and i assure you i like how you try to find out solution when i need some expert help. so no worry at all