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Thread: Troubleshooting "No RPM" indication

  1. #1

    Troubleshooting "No RPM" indication

    Hellow Trevor/AFS,

    For my 1st engine start, I didn't have any RPM indication. As part of my troubleshooting procedure later on in the week, what do I need in order to manually excite the RPM sensor - a magnet, ferrous material, other? I've got the RPM sensor that screws into the side of a slick mag and has three wires (red, white, and black).

    What voltage should I see at 'RPM V+' (Pin 31 of the sensor harness)?

    Is 'RPM GND' (Pin 16 of the sensor harness) tied to the ship's ground?

    What is the behaviour of 'RPM SENSOR (Pin 32 of the sensor harness) when it's triggered - low voltage, high voltage, other?

    Anything else you can think of I should check for?

    Thank you,
    /\/elson

  2. #2
    Hello,
    You should see 4.5 volts on the red RPM+ wire (pin 31)
    You won't see anything using a meter to indicate RPM. It is a square wave that is generated, so only a scope would allow you to see it.
    To test the rpm sensor first go into Instrument Calibration and select the RPM page. You will see a pulse count at the top of the screen. Use a magnet and brush it across the RPM sensor (removed from the mag). You should see the count increase each time you move the magnet across the bottom of the sensor.
    ---
    Trevor Conroy
    Technical Support
    Advanced Flight Systems
    Support@Advanced-Flight-Systems.com

  3. #3
    Fantastic! - Thanks Trevor.

  4. #4

    Testing Results

    Hi Trevor,

    I found the problem: the GND and SENSOR wires were reversed. Unfortunately, that did not resolve the problem.

    For "normal" EFIS ops and the sensor plugged in, I measured 5.04 volts for POWER. As soon as I passed a magnet in the proximity of the sensor, the SENSOR line went to 5V and remained there despite either removing the magnet or reversing the polarity of the magnet.

    For the "calibration" EFIS mode, I measured < 1V (I didn't write the actual value down) on POWER and while passing a magnet over the sensor, the count did not increase.

    For the sake of completeness, I reinstalled the sensor and cranked the engine while the EFIS was on internal battery. The RPM indicator remained at zero.

    This is f/w 8.03.28, on an EE-4500.

    Are the next steps to just replace the sensor or should I also send in the EFIS for inspection? Any other suggestions?

    Thank you,
    /\/elson

  5. #5
    It sounds like you need a replacement RPM sensor. Please contact Tricia for a replacement.
    ---
    Trevor Conroy
    Technical Support
    Advanced Flight Systems
    Support@Advanced-Flight-Systems.com

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