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Random motor failure Radcity 5+

Started by Larryfell, November 11, 2023, 07:55:35 AM

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Consistent problem. Random occurrence. Random solution. After ride, I store the bike in my garage. Next day the bike powers up and all displays and actions work but the motor is dead.  Within the next 12 to 24 hours the bike magically powers up for a ride.  The motor never faulters/dies while riding/traffic stops.  The bike fails about every fourth or fifth attempt to ride. After a few more episodes, I followed Rads on line checklist for solving this problem (disconnect battery, power drain, brake cables, tail light and hub cable). This technique works about 50% of the time. Letting the bike sit in the garage for 12 to 24 hours fixes the problem 50% of the time. Eventually I will damage the cable connectors. Please help.


This happens with my Radcity3 ST. I power it down and back up. I will start getting power to the motor after doing this 2 or 3 times. I took this in to the Radpower bike shop for service and had them look at it. They said they couldn't find anything wrong and suggested the power off-power on solution. On one occasion, it was a loose connection from the handle bar controls, so do check your wire harness connections.

I also occasionally will not be able to get my lights to turn on, but get power to the motor. I mounted a secondary headlight for those times when I can't get the lights on. It usually resolves itself by the next time I ride.


It sounds like condensation, to me. One morning I got my Radrunner out of the garage and rode half a mile to a store. When I started home, it wouldn't go when I tried to go from a stop sign. I walked it across the road. For the rest of the day it ran fine. It happened another day, after going half a mile to a store on my first ride. It had started the day after I rode on wet pavement.

I figured my aftermarket controller had picked up droplets thrown up by the front tire. In the garage overnight, it would condense on the power transistors, where it wasn't serious. In my first half mile, they would warm and moisture would recondense on more sensitive circuitry. A moment later, that circuitry would also be warm enough to stay dry.

I opened the case. I didn't see moisture, but a hair dryer fixed it until the next time I rode on wet pavement. RTV solved the problem.

The throttle always worked on my Radmission, but it was often slow to respond to button clicks, resulting in missed shifts. I hadn't ridden on wet pavement, but eventually I popped out the rubber plug on the controller case, inserted a vinyl tube, and for an hour fed it air that my compressor had dehumidified. It was great for more than a week, then got worse and worse. Dry air worked again. Apparently, this controller was so sensitive that humidity could make it act up. I bought an aftermarket controller and had no more trouble.