Step by step.
1. disassembly the scooter
2. take out controller, display and acceleration. Greetin box also.
3. keep the big round connector with 3 big pins and 5 smalls pins. Cut it from original controller.
4. buy any brushless controller with 36V and minimum 300W with acceleration. Could be with some display also.
5. Make the connections from new controller with big round connector. Keep in mind that the 3 big pins are for motor 3 pins. The 5 smalls pins are for hall sensor, 3 pins are matching the colors of motors connectors and more 2 pins, black and red for powering the hall sensors. (Actually a simple 3 transistors who detect the magnets)
6. Make connections to acceleration w/ or w/o display, usually the controller have the compatible connectors for acceleration (3pins) and with display may be in total 5 or 6 pins, depends which type are.
7. Connect the battery to controller by one big connector with 2 wires, black and red.
Until now everything are ok and the scooter must work fine.
The controller have more wires, with connectors or not, but this is the minimum necessary for work. Also, the controller must have two wires with one compatible connector each, for learning. With this two wires connected together the controller learn the sense of rotation of the motor, use it to set the proper direction of rotation.
Any of remaining wires could be for break, (the motor must know when to stop), for lights (36v!!!, use DC 2 DC converter) and many wires. All of them are optionally and could be or not used.
P.S. Sorry for my English, I try to do the best. Enjoy riding! Don't steal any of scooters, they have a serial number and it's easy to create problems. To view images REGISTER or LOGIN for full access.