i dont know the wiring diagram for the crown vic. but an easy check, unplug the blower motor harness and turn then turn on the blower and see if the fuse blows. if it does you have a short in the wires somewhere, so you will have to follow them till you find the problem. Second if it dosent blow your fuse then replace your blower motor its probley going bad and drawing more power than its supposed too!
It is possible that there is a bad ground or open wire - I have attached power and ground distribution wiring diagrams specific to a 2001 Crown Vic.
You did not mention which specific fuse blew, however, on a quick look for commonality I found on power distribution diagram 3 you can see that the Gray/Yellow wire supplies power to both fuse 16 & fuse 18. It splits and the Brown/Orange wire for fuse 18 supplies power to the Blower Motor and the Violet/Orange wire for fuse 16 supplies power to many components among them the DRL module and the Multifunction Switch. It is possible that a break in any of those wires could possible be your problem. Just a thought....
You more that likely have a defective blower motor or defective built in voltage spike suppressor allowing EMF generated by the blower motor to cause a voltage spike and current surge After looking at the diagram , I don't see how either of the wires being open could cause your symptoms. Only other thing I can think of would be a short in your central junction box . I agree with the suggestion by Pletchaj .
I'm sorry too Pletchaj for not stating your post was great and that I was expanding on your possible short theory - I got distracted looking at wiring diags and the 6 year old frantically jumping up and down beside me pointing at your Bender avatar (he just loves it!)