Originally this flasher unit was a hot wire type with a purely mechanical function. It did not matter therefor if it was fitted to a positive or negative earth car.
Current supplies (May 2014) appear to be solid state electronic. There is an instruction sheet supplied which suggests the wiring is thus:
Wiring B = X =Green P = P = LightGreen L = O = Green/brown
The instruction says that if the indicator lights do not flask on a positive earth car swap X and L and all will be well. This is fine in part as the flashers will work but our experience is that the warning light will flash continuously with the ignition on whether or not the indicators are operated. Not so good!
We suggest customers with Positive earth cars purchase GFU2101 which is of the hot wire type and not solid state and will work fine. As GFU2101 has screw connections some wiring alterations will be needed.