Battery fuse

A simple trick to finding a short is to replace the blown fuse with a pair of spade terminals, then use small jumper wires to connect them to a 12 volt light bulb. A brake light bulb works well. When the circuit is live and the short is present, the bulb will be full brightness and hot so be sure it's not laying on the carpet or against a plastic door panel. Now you can unplug electrical connectors and move things around to see what makes the short go away. When it does, the bulb will get dim or go out.

The sparking is from drawing high current just like an arc welder would do.

If that's the big bolted-in fuse, like a 100 amp or larger for the generator, you may have two or more shorted diodes. Unbolt the output wire from the back of the generator, then see if the short is gone.

[quote]I had my car on nd I was bumping my radio I have a 130amp alternator I have my car at 2000rmp to keep my amps up nd then out of no where POP my battery fuse went out[/quote]

Sounds like you have the usual problem of trying to use too much stereo for the electrical system the car was equipped with.

Sounds like I'm confused as to how this is happening. You must never ever remove a battery cable while the engine is running. To do so invites real expensive damage to computers and the generator. I assumed you were seeing a big spark when reconnecting a cable with the engine off and that's when the fuse was blowing. If that's really the case, do the procedure with the bulb in place of the blowing fuse.

Next, what do you mean by "bumping" the radio? I took that to mean you're moving it around or tapping on top of the dash board. A bared and shorting wire behind the radio will not blow a large fuse. The main power and the memory circuits are protected by 10 - 20 amp fuses which are the ones that would blow.

Wrenchtech makes it sound like you call "bumping" the radio raising the volume. AC Generators are physically incapable of producing more output current than they are designed for. Your car originally came with about a 70 amp unit and any fuse in the output circuit would have been large enough to handle that. If you switched to a 130 amp generator, only its capacity would be higher. It would not deliver any more output current than the car's electrical system called for. Now if you add a hard-of-hearing audio system and turn up the volume to entertain your neighbors, the larger generator can intermittently produce more current than the original fuse can handle. You would need to install a larger fuse. At issue then is if the rest of the wiring going between the generator and battery is fat enough to handle the additional current. In the early '80s, for example, Chrysler came with one of three alternators and the fuse link wire size was appropriate for that alternator. It was easy and common to install a replacement unit with higher output but that left you with the original fuse link wire which wasn't large enough. Under all driving conditions the larger alternator will still produce just the required output and no more so that under-size fuse wasn't be a problem. There's only two times the output can go high enough to blow the fuse. The most common is when someone performs a professional load test to see what that maximum output is and that can exceed the fuse's rating for a few seconds. Fuse link wires won't burn open that quickly; regular bolted-in fuses will. The other condition is when added-on equipment draws more current than normal. Since the bigger generator has the capacity to meet that higher demand it will produce it and blow the fuse.

In the case of the Chryslers you just replace the fuse link wire with the larger diameter one appropriate for that system. The rest of the wiring was already sufficient to handle the output of any alternator you could install. I don't know if that applies to your car but the fuse or fuse link wire will always be the weak link in the chain so the rest of the wiring can handle more current. I doubt though the original wiring in a '90 model could handle 130 amps but the entire electrical system should never be drawing that much current continuously.

So the question I have is, ... Do you really have a problem with the electrical system, and if not, what are the exact conditions that are causing the fuse to blow?

Only a major shorting would blow the main fuse. Any other wires smaller the main fuse (130 A, which is rather high capacity) would result in the wireharness going up in smokes, maybe the vehicle as well.

If the alternator had gone bad due to age or other factors such as excessive current draw and caused internal shorting, then the main fuse would blow. If you are still blowing fuses whan reconnecting the battery terminals, disconnect the alternator main wire and test for a start.

That's a warning that the alternator is working too hard. It wasn't designed to power a couple hundred watt stereo.

What Wrenchtech means is a 130 amp generator is not intended to deliver 130 amps continuously. That is its maximum so it can meet intermittent demands while still being able to recharge the battery and maintain system voltage to proper levels.

If the insulation on the wire melted, the generator got hot. If it is rubbed through from touching something, that is a simple routing problem that caused abrasion. This doesn't sound like what happened on your car but the third possibility is there was a tiny bit of corrosion in the output connection or the nut was loose. That would create a small amount of electrical resistance which would lead to heat buildup and eventual burning away of the plastic insulator where the output terminal comes out.