I have just gone through the same thing myself, unfortunately I managed to "kill" the MOSFET on Fan 0 where I was trying to install a cooling fan that came on when the head temperature exceeded 50C, but that's another story!

If I am not mistaken doesn't the slider control FAN1 not FAN0?
When you activate the slider does an orange LED come on near either the FAN0 or FAN1 header?
Have you tried control through the LCD Control / Temperature / Fan Speed (or something similar)