140 amp breaker blew?

Fuses that large are normally bolted in. The first thing to consider is those connections must be perfectly clean and tight. Just a little dirt or corrosion there will cause heat build-up when current flows through them. Fuses are thermal devices, so the heat generated by bad connections can cause a fuse to blow when it normally wouldn't.

Next, AC generators are physically incapable of developing more current than they are designed for. The two sizes used on your model are a 100-amp or a 130-amp. Neither will develop more current than the fuse can handle, however, if someone replaced the generator with an aftermarket replacement that has a higher maximum capacity, that can exceed the fuse's rating, but only under one condition. That is during charging system testing.

Regardless of how much current a generator is capable of developing, it is always only going to develop exactly how much the vehicle needs to run the electrical system and recharge the battery, and no more. If the electrical system needs 79 amps, even the largest generator in the world is only going to develop 79 amps. The exception is during the "full-load output current test" part of the charging system test. That takes just a few seconds; just enough time to read the value, but that can be long enough to burn open a fuse if the generator is capable of developing more current than the original one did. Most older models, and a few current ones, use a fuse link wire for this circuit. Those take some time to burn open. They act like a slow-blow fuse, and will usually survive the full-load output current test if a larger generator had been installed.

The next most common cause for this fuse to blow is when work is done to or within the area of the generator's large output terminal on the back. It's always recommended to disconnect the battery's negative cable first to prevent this accident, but in the name of saving time, many of us don't do that. Also, a lot of newer cars have "got'chas" built in that can cost thousands of dollars to fix at the dealership simply from disconnecting the battery. Most mechanics now are skittish about doing that, so we work on the electrical systems live and take our chances on blowing fuses. If a wrench bumps the generator's output stud and a metal bracket at the same time, that puts a dead short on that circuit. That 140-amp fuse blows to protect that.

The last thing is the least common cause, but is actually why the fuse is put in this circuit. That is a shorted generator output circuit. All AC generators have at least six "diodes", and sometimes more. Those are one-way valves for electrical current flow. During normal operation, think of the generator as a pump, but for electricity instead of water. The diodes become "forward-biased" and let current flow through them out to the battery and electrical system. When the engine is off, (generator not spinning), the diodes become "reverse-biased" and block current from flowing out of the battery and through the generator to ground. The diodes are always in two sets of three. If just one diode shorts, it reduces the generator's ability to develop current by exactly two thirds, so in your vehicle, all you'd be able to get is close to 33 amps. The three diodes in the other set will still block current from discharging the battery when the engine is off. It's in the rare event you have two shorted diodes, one in each set, that you have a dead short. In over 45 years, I've only run into that twice, so it's very uncommon. Also, I don't really suspect that here because a shorted diode is never an intermittent problem. They're either good or shorted, period.

What I would do now is keep an eye out for any unusual symptoms that occur just before the fuse blows again. Flickering light brightness would be the first thing that comes to mind. For that I'd start by looking at the terminals on the back of the generator to see if one is positioned close to something metal. Look at the plastic bushing the output stud is on to see if it is melted or burned away. That would be a sign the terminal was loose on that stud. That will cause heat build-up, which leads to a worse connection, which leads to more heat build-up, until that bushing melts.

Let me know if that helps or if the fuse blows again. I have a trick for finding shorts, but in this case it works best if you can catch it while the problem is occurring.