How to disassamble an external plug ?

Step 1 :

Unscrew the cable gland with watertight seal 

Step 2 : 

Hold firmly the plug end and unscrew the tubular part of the plug.

Step 3 : 

The phases of the hydrogenerator should be connected to the pins 1, 2, and 3.

As this is a 3-phases generator, there are NO order between the phases. Usually the fourth pin (identified as ground) is not connected.

Check that the inside of the plug and cables are completely dry, with no corrosion at all and that the wires are well tightened.