Hello again,

I have purchased a higher amp output alternator for my trooper. It was recommended to upgrade the wire to 4 or 6 gauge. I have a couple of questions about it:

1) How necessary is this?

2) Where can I find a high amp fuse ( I saw a kit on eBay that had a 250amp fuse, but it was $50!!)

3) I looked at my wiring diagram and it looks like the alternator and battery white wires go to the fusible link box that is behind the passengers side headlight. Is fusible link what I should take out and put in the large fuse at?? It also looks like this is where the power goes out to the rest of the car. This just seems a little bit harder then I pictured.


Any help would be appreciated. I will be taking a long trip soon and need to work out any bugs now.

I think that I would go with the manufacturer's recommendation as far as the wire goes. They said that for a reason.

Yeah I do plan on going with the larger gauge but I'm not sure where I need to put this larger gauge, also not sure what to do with the fusible link. It's hard to say what the fusible link is for, either to prevent overcharging from the alternator or to prevent the vehicle from drawing too much from the battery (the way it's wired seems weird to me). If the link is more for the alternator then it would seem that I should replace it with the big fuse. But if it's more for the vehicle drawing too much power from the battery then me putting a huge fuse on there might allow for other issues??

I suggest you find a good reference on automotive electronics. It will serve you well now and in the future.

An alternator cannot "overcharge" unless the regulator is not functioning correctly. An alternator also does not put out more amperage than is required from the system. I.e if your max load your truck could ever possibly draw is 65amps, your 200amp alternator will never put out more than 65amps.

In general, a vehicle draws current from the battery, with the alternator providing the juice to keep the battery charged and to provide current in excess of what the battery can provide for peak draws (winches, stereo, lights, ect). It is not quite a flow-through system, but for the purposes of this discussion, consider it as such.

In your case, you should upgrade whatever the heavy wire from the alternator is. This should be on some sort of ring terminal on the back of the alternator. If it goes through the fusible link, so be it. I don't feel like looking up the wiring diagram right now, that is your job. :-) But, it should go to either some sort of power distribution block, the battery or a fuse box. In general, you don't really need to put a fuse on the charging wire for the alternator, but there should be fuses between it and anything that requires amperage. I would suspect the fusible links are for things like the headlights, which need considerable amperage, not on the incoming wire from the alternator.

Good Luck,
Michael

As Always Michael your posts are most helpfull!

That really cleared some things up for me. I wanted to post the wiring diagram I have from my Hayes manual. I still need some help figuring out what wires need to be upgraded and how I should go about doing it. The fusible link box is in a very annoying place and appears to be welded to the frame. So I am unable to get below it to access the wires that go to the big fusible link. Is there a trick to getting in there? Also I would assume that all the connections to the fusible link box are special crimped on connections that I will be unable to use again for the larger gauge wiring.

It appears that your fusible link box protects (A) the high beam relay, (B) low beam relay, (F) lighting relay (gauge clusters) and lastly, (F again) the main relay which feeds your ECM and various sensors. There's more interconnectivity than I've stated, however, that's it in a nutshell. You don't need to upgrade any of that. I'm looking at the same junky "typical wiring diagram" you are. According to this, you have a white wire running from fusible link F to the + POS side of the battery. That's the only wire I could see which might need the upgrade. Normally, you'll have a big hot cable running from the alternator to a lug on a large amp fuse (100 amp or greater) located on the end of your under the hood fuse panel. From the other lug on the big fuse, another hot cable runs to the battery. When that fuse goes belly up, your alternator will no longer charge the battery. Looks to me like the white wire serves that purpose. I like Isuzus and their ruggedness, however, some of their engineering (primarily electrical and fuel/emissions) leaves a lot to be desired. What amp alternator did you upgrade to? It would have to be pushing 300 to be calling for a 250 amp fuse. <img src="/forums/images/graemlins/lol.gif" alt="" /> Like the other reply stated, your electrical needs, relays, starter, etc. are only going to draw the current necessary for them to fully function if everything is in order. The wire recommended to be a 6 or 4 gauge; which one is it? The white wire to the battery?

Yeah I would agree with most of what you said. The alternator I got is 200amp. It seems to me that I would need to upgrade the wire all the way from the alternator to the battery (highlighted in red on the picture above). I looked up an alternator wiring kit on eBay and it basically consists of a 4 gauge wire and a 250 amp fuse and it's listed as a 200+amp alternator kit. So I would have to say that instead of a fuse Isuzu decided to use a fusible link. So According to this post:

http://www.4x4wire.com/forums/showf...&sb=5&o=&fpart=1

The link is rated at 26 amps. That seems incredibly low to me. I also still have the delema of trying to get under the damn fusible link holder that is freaking welded to the frame. Anyone done anything with these fusible links? I can't be the only person who has upgraded their alternator??



I'm starting to run out of time on this project before my big trip. If I am not drawing anymore power then usual with this new alternator I should be able to just leave the stock wiring in place and not have anything burn out correct? I can spend some time trying to upgrade the wiring when I have more time and I actually install some devices that need the extra load.

OK just spent some time on this. I managed to get the Fusible link holder off the welded piece, it has these 2 incredibly annoying plastic tabs that hold it in there... Anyway it looks like the wire directly coming off the battery goes to one side of the fuse link. Now the other wire off the fuse link looks to go all the way over to the damn fuse box on the other side of the engine bay, then another long white wire come back and goes to the alternator!! How freaking annoying!! How should I proceed? I really don't want to run two long wires all the way to the fuse box and back. Seems like it would be faster to go from the alternator to the back of the engine and around to the fuse box directly, then just use the wire coming back in front of the radiator then through the fuse link and to the battery..... Still a lot of damn 4 gauge wire to get!

The short answer is if you are just swapping out the alternator and you need it for a trip, don't worry about it. You don't need to upgrade wiring if you don't have things that use high amps.

After looking at the wiring diagram, it seems like Isuzu is using the fusible link box as a distribution block of sorts. It provides power to the lighting circuit AND protects the rest of the electrical.

So, to fix this you could do it in a few ways. You could run 4ga wire directly to the positive post of the battery and remove the between the alternator and the fusible links. You could also probably leave the wiring as is, and add another 4ga between the alternator and the battery. The fusible links are still getting power from the battery and one of the links is protecting the battery side of the circuit. You don't need circuit protection on the charging side of the circuit.

I think my prefered route would be to add the wire to the battery and leave everything else. That way the lighting circuit can share the load when the engine is running, instead of running 100% of the amperage through one side of the supply to the fusiable links.

But, when you add things (stereo, lights, winch ect) they will need individual protection related to their individual loads (this is where you could use the 200A fuse on the winch, for example), but they will need to be wired off the positive post of the battery (either directly or through an appropriate distribution block).

Clear as mud?

Good Luck,
Michael

That sounds like the best solution to me! Just to be sure though if I just want to add the extra wire from the alternator to the battery, then there would be 2 wires connected directly to the alternator? The original wiring, and then the extra wire I just added. Then if I add extra items that require more power then I just need to connect directly the battery?

Thanks again Michael, you are a very big help!