Fatts,
the below is taken from endless-sphere and if you can supply 5 volts with your three wires one will be live, one earth and one signal, not sure if you get it wrong what happens though! I would guess the black as the earth first and then guess for which to apply the positive to first.
Good luck.
Daryl
"Checking the thottle is done in a similar way.
The throttle connector has 4 wires. Colors below are coming from the controller:
With power on, red should read around 5 volts.
Black should be near zero.
The white wire is the signal wire, and should vary from about one volt at zero throttle to about 4 volts at full throttle.
The purple wire will read battery voltage.
Colors may vary depending on model, but the measurements are the same. Measure all the wires if you don't know the colors."
