Hi Warren and
to the forum.
The very first Magic Pies
(MPI and MPII) had their controllers completely hidden inside the motor:
The "unused" yellow wire was used for reverse
and programming data on some controllers.
On the MPIII, MP4 and MP5, the controller is accessible from outside, as the cover of the controller is exposed to cooling air.
Early MPIII controllers had a plain cover as shown on the left, but later controllers
(Late MPIII onwards) had cast cooling fin covers as shown on the right:
Here are the wiring diagrams for the harness connectors:
If it's a recent Magic Pie the connections will be like this:
Hopefully this is enough information for you to figure out what each of the wires are for, but please ask if you need more details.
Alan