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Throttle problems

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    Throttle problems

    I have a converted cruiser with a front hub motor and twist throttle. When I rode it last I notice the throttle wasn't cutting out when I stopped twisitng it - the motor kept working. To stop it I had to turn it off at the display. This happened three times before I got to my destination. Each time the motor wouldn't cut out and the wheel spun at max speed. The next time I tried to ride, the throttle didn't work at all.

    We've tested the motor controller, battery etc and power is going through as it should and have checked all the connections etc. When I twist the throttle nothing happens.

    ​​​​​​I had thought it was a faulty throttle but I just connected a different throttle on the bike and when the display is turned on it immediately starts the motor, spinning the front wheel at max speed, without the throttle even being used at all. It seems strange that a new throttle would activate the wheel without being engaged.

    Is it likely the motor controller had a fault?

    Any help/advice would be appreciated. Thank you

    I think that is almost certainly a shorted throttle wire, someplace. In the wiring you left on the bike, not the wiring you changed with the throttle. That could explain why it started out intermittent. Wires tend to short a little, then more and more, as the false connection gets better with progressive damage.

    You need to find where and fix it, then the original throttle will probably work again, too.

    This is a dangerous symptom to diagnose! Be careful, please. Wiggling wires while letting it run is the dangerous way. Using a DVM to probe and check for shorts, is better. Finding damage visually, a kink, tight zip tie, worn spot, etc, is the place to start.

    Good luck.
    Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.


      Doesn't have to be a shorted throttle wire. I've found that if the ground wire is (edit) disconnected my thumb throttle while other two wires remain connected. , the controller spins the wheel at full speed,
      Last edited by HarryS; 03-20-2018, 06:41 AM.


      • HarryS
        HarryS commented
        Editing a comment
        Bad typo. The output pin on the Hall sensor inside the throttle will float up to 4 volts when the ground wire is broken. That tells the controller to go full speed. I've tried it on several different controllers.

      • max_volt
        max_volt commented
        Editing a comment
        That sounds normal. Without a ground the whole circuit will float towards supply voltage.

      • JPLabs
        JPLabs commented
        Editing a comment
        OK, thanks.

        So, BROKEN ground can cause this too.


      Perhaps a little more information would help... Hub motor, controller, display, old throttle and new throttle makes and models...then more accurate wiring trouble shooting suggestions could be given.
      See my completed Magic Pie V5 rear hub motor E-Bike build HERE.