GM External Controller Wiring

[Bedmountain]

I'm currently swapping my MP3 internal controller for the GM external 50A version.

Extending and attaching the hall, phase and battery wires is simple enough but I'm a little confused about the throttle and cruise control connection.

I stripped the end off my 4 plug GM wiring harness and used Bikemad's helpful diagram to work out the colours for each wire. I was a bit surprised that the battery (+) was orange and the cruise control was red given that GM made the harness and the controller and all the other wires seem to color match (Alan/Bikemad could this be an error in your diagram or should I go with orange = battery (+)?



I've taken a picture of the controller wires and the end of the wiring harness:

Connecting the orange battery (+) and the black battery (-) to the yellow plug seems obvious

at the blue plug do I just connect the cruise control (red) to the orange wire and leave the black empty or do I need to split the black (battery (-)) wire at the harness end and connect that to the other side of the blue plug?

For the throttle plug I can see where the green wire should connect but again do I run battery (-) to the black wire and what do I connect to the red wire on that plug?

Sorry for the noob questions - I thought this was going to be very straightforward but I can't afford to get this wrong and damage the controller....

Any help much appreciated.

[Bikemad]

Hi Ben, as far as I know, the diagram is correct. It was drawn after using an ohmmeter to check the continuity between all of the connections on my original MPIII harness. I did not cut the harness open, so I have no way of telling what colour wires are used inside the main 8 core cable.

I would double check the continuity between each of each of the eight separate wires and their respective connections on the multi-connector to make sure they are what you think they are rather than assume that the colours and functions are the same. By a process of elimination you should also be able to determine which of the eight wires is not used inside the multi-connector.

On the Throttle connector the red wire connects to the +5V wire and the black wire is simply a common battery - connection which is shared by all of the separate connectors.
On the MPIII harness these common ground connections are made internally inside the multi-connector so there is only one battery - wire for you to connect, and it should ideally connect directly to the main black wire coming from the controller connector block which goes to the yellow connector.

Alan