It sounds like the factory wired the lights with positive to their bases and negative to their center leads because they were incandescent bulbs so what polarity they ran on did not matter.
The turns signal flasher is polarity sensitive so in order for it to operate it will need to run on the same polarity as it received when the scooter was built.
Regarding the motor not running I suspect that might have something to do with the brake light polarity being reversed and the controller continuously receiving a positive high e-brake signal when the brake switch is off.
To try to resolve the problem I recommend switching the polarity between the DC-DC converter and the scooter's wiring harness back to its original configuration and then individually switching the polarity of the lamp holder wires so they are compatible with the new LED bulbs.
Forwarded by the moderator from an additional forum topic:
I have more information that may help with a possible diagnosis.
When I disconnect the 48V to 12V dc/dc converter there are no lights but the motor will run. If I then turn on the light switch, the motor will shut off. Also, if I hold the horn button on, there is no horn, but the motor shuts off.
Is there a way to eliminate the link between the 12V dependent items and the speed controller? There may be a +12V brake light wire that is connected to the controller and if it is disconnected from the controller that may help to accomplish this goal.
The brake lights, when functioning, come on from a signal from the controller. Right? Is that the connection? The brake light power wires run through the controller on some scooter and run externally from the controller on others so the brake light signal may or may not come on from the controller.
Only the 1157 tail/brake lights and the high/low beam headlight cannot be fixed by reversing the wires.
l am trying to solve for reversed polarity observed at the sockets of the scooters 12v lighting system. The scooter operates on a 48v battery pack. My lack of electronic knowledge and physical disability have been keeping me from digging deep into the wiring of the system. l have failed at all attempts to obtain help or a wiring diagram from the retailer, distributor or the Chinese manufacturer.
l took a chance and switched the positive and negative leads exiting the 48v to 12v converter. This worked spectacularly for all light sockets including high/low headlamp and running/brake lights, using LED bulbs in place of incandescent bulbs. All 12v powered items including the horn worked. The only problem was with turn signals not blinking.
l tried to ride the scooter after correcting the 12v reversed polarity only to find that there was no power to the motor.
l don't know how the dc/dc converter interfaces with the basic operation of the controller.
ls there a way to now correct the motor malfunction with maybe a couple of strategically placed relays?