Ive searched for days on these forums and on others and thought i should finally post about it. So recently this fuse has just started to blow at random times, usually the worst times possible like offroading. But I cannot force recreate it, it only blows when it wants. Ive looked over and under the whole thing and cannot find any bare wires. Ive tried flexing every part of the wiring harness and even spraying it all with water because it has happened while going through water but still have no results. I've ended up putting a 30a auto resetting breaker in place of the fuse but I would really like to fix the root of the problem. Any ideas of hidden wires im not finding or components that are connected and could short out internally?

Remind us of what year XJ this is, and what engine and transmission is in it.

Ahh sorry, 92 4.0 aw4 np242

If Firestorm500, or some other antique restoration experts, catches wind of your thread they will give you a hand.

Hang in there.

Bump

I searched and found many experiencing the same issue but no resolution in any of them. Just curious, could this coincide with your aux fan kicking on? It sounds like the aux fan is run off a subsidiary fuse that is powered by the #15 30A and could be introducing just enough load that, combined with another dodgy connection, could trip the 30A. The problem with this scenario is that it would require multiple shorts on separate circuits linked to the 30A through different fuses. Otherwise, the smaller, subsidiary fuse would pop before the 30A. My understanding is that the ECU is directly powered by #15 but other things like O2 sensors, aux fan, fuel injection, and fuel pump relay are all powered by fuses that derive their power from that 30A.

the above sounds plausible. All it would take is some moisture / water at the point of contact and as soon as it triggers on, the water makes it trip.

If you are talking about the first big fuse in the fuse block on the pass, side front fender than maybe this will help. I had the same problem, and I found that the fuel pump relay has 2 green wires running from it, one goes to one side of the ballast resistor on the drivers side inner fender near the hood hinge, the other side of the balast resistor goes down and back to the fuel pump, the problem I had was the wire from the relay to the balast resistor had becone brittle over the years and cracked and would sometimes touch something abd short and blow the fuse. I just ran a new wire and fixed the problem. The other green wire from the relay I never found where it went so I just left it cliped off, hope this helps.

did you find what the issue was?