The Fantastic fan has just a few electrical parts. I have fixed mine not starting the fan (corroded contacts in the rooftop dome pin switch), but a short circuit is something else. Is the correct size fuse in the fusepanel slot? The first thing that happens when you activate the fan assembly is that the lid lifting motor starts turning to open the dome lid. Could this mechanism need lubrication? You should be able to pull down on the lid knob, turn it, and move the dome lid manually. The lid motor could be frozen up, or be shorted. Parts are available on e-trailer:
https://www.etrailer.com/dept-pg-Accessories_and_Parts-pm-Fantastic_Vent.aspx
You might be able to disconnect one of the wires on the lid lift motor to see if that is blowing the fuse.
As with all fuse blowing problems, you are probably going to need a good supply of fuses until you solve the problem.
After the lid is lifted some, the rooftop dome pin switch should make contact and turn on the fan.