Amiga 4000 Desktop Fan?

[Ilwrath]

Ok whats the deal with the 4000. The Fan should blow air in or out?

Yes.  Supposedly, some originally blew air out the back of the case, but most (including all stock ones I've encountered) suck air into the case through the power supply.  

The best solution I've seen is to open the power supply and physically face the fan in the opposite direction.  Then, remove the faceplate from the 5.25" bay and install an intake fan in that position.  (Thereby bringing cool air in the front, and blowing hot air out the rear of the machine)

[Ilwrath]

Wouldn't it be easier to switch the fan's power wires around so the power is reversed or is there something special about the shape of the fan?

Well, that would change the direction of rotation, but I don't know if the stock A4000 fan is unidirectional.  It might make more noise or be more likely to fail if you hook it up backwards.  (When I had mine apart, instead of facing the fan in the opposite direction, I replaced it with an Enermax whisper fan that I pointed outward.)