Hi back again. Can you do this:
Make sure the Variac is unplugged from the mains
(1) remove wire from terminal 6 and connect it to terminal 4
(2) remove the wire from terminal 3 (wiper) and wrap the exposed end of the wire in tape.
(3) Put the wiper more or less in the centre of its travel.
Turn the mains switch on the variac to on.
If you have a switched wall socket use that.
If not, plug the Variac plug into the mains but be prepared to pull it out imediately if there is any sparking, loud hum or any other indications of stress.
Let me know how it goes.
PS: I am expecting nothing to happen at all- if I am right the Variac will not be energised.