I trust it is the 85 that you are refering to.
The defogger is tied into (relatively speaking) the tailgate motor via a orange wire between the defogger timer and the rear tailgate switch.
The individual black wires on either side of the tailgate should be the defogger wires. Guessing, don't know of any other individual wires. All others I know of are at least in pairs.
As for the fuse above the 30 circuit breaker, those wires might be rubbing underneath along the driver's side frame rail near the back. That 20amp fuse controls the park/tail lamps and fogs.
With all this in mind, I would check all the wires right there at the fuse box first, seems how the offending fuses are in between the two tailgate breakers.
1987 Jeep J-10 (stock+liftgate)
1991 Geo Storm GSI
2006 Pontiac Montana SV6 Sport