Hi Vince and
to the forum.
Unfortunately, the MPIII controllers don't have the brake or throttle failure bypass mode so the half throttle function will not work.
As the new throttle hasn't cured the problem, it could be either a faulty wiring harness or the controller itself.
You can perform a simple test which will bypass the control harness, brake switches, throttle and cruise controls and simply checks the motor, controller and battery circuit by disconnecting the main control harness and then bridging two throttle contacts with a piece of small diameter wire, I used a reshaped paper clip as indicated here:
Don't force the wire into the sockets as this can open the contacts up, resulting in a poor contact with the pins when the the main harness plug is refitted, you only need to touch it against the two contacts to hopefully make the throttle run at full speed, confirming that the motor, controller and battery are all OK.
To avoid accidentally shorting out the wrong sockets, and causing possible damage, you can place a piece of masking tape
(or similar) over the other sockets to ensure the wire does not accidentally enter the wrong socket.
As it states on the diagram,
make sure the bike is secure with the wheel raised off the ground before you insert the wire and keep hands and loose wires etc. safely away from the wheel and tyre! Please note:
The power must be turned on before the wire is inserted into the correct sockets or the motor will not run!If it doesn't run during the above test, I would say the controller or motor harness is faulty and will need to be replaced.
Alan