So I have the tanker acting like a tanker after checking the box in the design screen (thanks Jacen), I get it to come up with the sub-options to refuel. . . . But it still won't refuel.
I stopped all orders and even conditions to stop it from thinking of moving, but for what ever reason I cannot get this thing to take on fuel. I added the tanker to another fleet, tried the option to refuel from tankers, the fleet moved and went to the location. . . didn't refuel.
Ok, tried join and refuel target fleet. . . it joins the fleet. . . doesn't refuel the empty survey ship.
Edit: Maybe something influencing it, when i ticked the box to make it a tanker, it says "minimum fuel set to zero" in the bottom right that I'm not sure how to influence.