Speedo inop - 1996 VFR 750

Discussion in 'Mechanics Garage' started by VT Viffer, Oct 31, 2014.

  1. VT Viffer

    VT Viffer New Member

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    Hey guys, it's me again.

    My speedometer still will not function. I have tested that I am getting 12v at the sensor and at the back of the gauge cluster. I have tested for continuity on the pink wire to the back of the cluster. I took apart the cluster and located a burned resistor on the PCB. I have replaced the speedo sensor with a used unit and transferred over the PCB and speedo motor from another cluster to my own. I still do not have a functioning speedo.

    It was working fine before the over-voltage event that cooked my CDI.

    What are your thoughts?
     
  2. rjgti

    rjgti New Member

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    did you do the live test and measure pink wire at speedo board, backside of wire in, ign on and check for 4.7-5 vdc while rotating tire?
     
  3. VT Viffer

    VT Viffer New Member

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    I did, but plan to do it again. I have read that a DMM is not the best for this test, though. Readings were inconsistent, and not to spec for both the original and the used replacement sensors.
     
  4. rjgti

    rjgti New Member

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    dmm will be fine, make sure to rotate tire in the right direction for test
     
  5. VT Viffer

    VT Viffer New Member

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    Well, I've been sick all week and standing out in the cold and dark to troubleshoot an electrical problem didn't happen until today.

    I tested the sensor signal at the back of the cluster again, hoping to get a signal, which I didn't. I was bummed.

    Figured it couldn't hurt to swap the original sensor back onto the bike to see if the used one I had sourced was dead (this was my first attempt at a fix). As soon as the original sensor was on the bike, the speedo needle jumped (and stayed) at 35mph when the key was switched to 'ON'. On the center stand and put into gear, the needle began to swing upwards!! It works! When the ignition was switched off, it fell back to ~10mph.

    Well, that's a good sign, I guess! But there is still something amiss...

    The next step was to remove and disassemble the cluster (again), pull the needle off, and reinstall it back on the pin when the speedo was energized, pointing at zero.

    So anyway, I have a working speedo again. The issue was a fried resistor on the PCB behind the speedo (I don't believe that the speedo 'motor' was ever an issue), compounded by a burnt up speedo sensor that I replaced thinking it was the original issue. Once the original, functional sensor was re-installed, the repaired speedometer began getting a good signal.
     
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