2002 Ford Ranger Blower motor-blowing fuses

Ok, so the heat and air conditioning worked on this truck worked when I bought it. Here recently both the the heat and air went out. I found the fuse on the interior fuse panel. (10amps) I replaced the fuse. Everything worked for a couple days, then the same fuse blew again. Now it blows 10amps fuses with in minutes of me changing them. I replaced the blower motor and replace and put a 15amp fuse in. Again, everything worked for a little while. Then when I started the truck this morning it blew the 15amp fuse as soon as the truck started. How do I fix this problem? Need air!