xb700li controller

hey guys,
i am trying to figure out my sister in laws scooter. i am getting 52 volts out of the big black wire coming out of the controller. when the black wire is unplugged everything works on the scooter with the exception of the rear wheel motor. when black wire is plugged in it pops and shuts everything off. unplug black wire and unplug battery fuse wire and plug back in and everything works again. i am assuming the controller is shorted out but i wanted to see if anybody on here has had that problem. also if the controller is shorted out, is the hub motor shorted out also. is there any way of checking the hub motor? thanks, ron