Gew9000

Hi there all I have just got my hands on a gew9000 winch which I brought as spares or repair the bloke said it just stopped working one day it didn't come with any battery leads which I have I no where the earth lead connects to the winch but am stuck on where to connect the positive lead on the winch so I can try it as I have read on a few forums that most problems are bad earth connections so any help would be appreciated