I did not say everybody should remove their throttle, but maybe her son should as he does not yet know how to manage it. It sounds like this should be taken to an expert like she asked, to get it repaired and instructions how not to not damage it again. I am not convinced that an “electrician” is the right expert for this job, an electronics repair person would be better. My electrician skills are useful, but my limited knowledge of electronics pretty much dead ends my ability to complete the diagnosis. She needs an Ebike experienced technician to sort it out. From experience I have wasted a lot of money just guessing and replacing. Since the company is defunct it goes forward as a custom E-bike, as are most of mine, (I have only one factory bike and I upgraded the controller/display to KT to get a real display) Replacing the whole system as described is sound, but that phase wire fault could mean a damaged overheated motor, it would be cheaper in the long run to replace the entire system including the motor if so. Perhaps all the components in the system are substandard, a Bafang or other quality hub might have shut itself off before this, or it could have handled the full 20 amp load longer. Or did the cheap controller actually limit it to 20 amps?
Finally, I have throttles, but I am into using motors to assist my pedaling, where I live there are many hills I would walk without my motors. I use the throttle primarily to assist launching recumbents up hill and other difficult situations with the bikes.
As a young person who saved up his money to buy an e-bike he needs training on the use of electric motors, and or experience. This is the experience version. He spent his money and now he has a broken bike. Without the throttle he may have discovered his bike is underpowered but he would likely still have it to use. That his mother is running along beside him sounds like he might be quite young.
