Ramps 1.4 d2 pins for12v extruder fan, polarity? (no replies)

Hello

I am almost finished with my prusa i3 build (graber) lasercut edition, with ramps 1.4 electronics and I have a quick question:

Does the 12v extruder fan that is supposed to connect onto d2 12v aux pins have polarity? If so which way?

The prusa i3 rework instructions in reprap wiki suggest to plug it into d2 but no indication of polarity

Thanks in advance.
Rui