According to the FSM for your TJ the following is a list of circuits energized by the #7 fuse circuit:
1. Antilock Brake Controller,Antilock Brake Relay (in the PDC)
2. Rear window defogger relay (in the PDC)
3. Park/neutral position switch
4. Back up lamp switch
I'd start checking the related circuits that way you will be more than likely be able to narrow down the search for the cause of the short circuit.
*WHATEVER YOU DO DON"T PUT A HIGHER RATED FUSE IN THE BLOCK, THIS COULD START A VEHICLE FIRE*