Alternator Upgrade, do I need to upgrade alternator fuse?

Hello,

I want to upgrade the alternator in my 2007 4cyl pre-runner to a 200A model. I'm planning to also upgrade the big 3 wiring, but I'm not sure if I also need to upgrade the alternator fuse as well. The current fuse is 120A and I can't seem to find anything larger than 140A. Any thoughts on that?

John

 

It depends on how you do your wiring.

Whatever it is you're adding ("additional gear") that needs more juice than the factory alternator can handle, if you add it downstream of the factory fuse (the 120A alternator fuse), you will need to replace that fuse one way or another. There are not, to my knowledge, any commonly available fuses that fit the factory fusebox location higher than 160A (and even 160 is kinda hard to find), so if for example you are trying to pull 200A through it, you will need to replace that fuse with a solid link and add a properly rated fuse somewhere between the alternator and the fusebox feed. You will also need to make sure that your new Alternator -> Fusebox wire is rated to handle the increased load. This will likely lead to physical modification of the fusebox. I also do not recommend doing it this way if you're really feeding something big - the fusebox internals were designed with the factory specifications, and if you're booming or winching, popping that fuse will kill the truck entirely.

Another option is to run a second (parallel) cable from the Alternator directly to your Battery lug and then to a bus bar/feed system for your additional accessories. This run should also absolutely be fused at an appropriate capacity for the draw of your additional gear, unless you individually fuse your additional gear between the gear and the battery (whether by using a fused power distribution center, bus bar, inline fuse, etc).

The only thing on these trucks that should ever see an unfused connection directly to/from the battery is the starter or winch (or possibly whatever other esoteric device you might be adding, if the manufacturer recommends it).

I have a fairly extensive writeup or two on the core electrical system of the 2nd gen trucks. They're a little cluttered with discussion/BS but I've gone through over time and made edits for clarity etcetera. There's some pretty good info if you have the time to pick through them.

https://www.tacomaworld.com/threads/1gr-fe-wiring-overhaul-a-slow-descent-into-madness.712981/

Note specifically Post #16, which has a diagram of the circuit feeding the fusebox from the alternator, which then feeds the battery in the stock configuration. The Big 3 method in that thread is different than the most common one you find on TW and elsewhere, which actually removes the fuse protection from the circuit entirely by altering the factory wiring path, which is something that works well enough for a lot of people but is not IMHO a great way to do it. Toyota spent the money to fuse everything, if it wasn't necessary, they wouldn't have.

Here is a companion post for the Big 3 method I used, with a lot of discussion, links, and some other folks doing it this way:

https://www.tacomaworld.com/threads...l-v6-get-ready-for-spring-maintenance.734046/

 

Sorry for the long delay in responding. Thank you very much for your detailed reply. I realize now that I do not need to replace the 120A breaker. I want to split off the feed from the alternator so that I can drive a battery charging system for the back of the pickup. I'm turning my Tacoma into a minicamper and want to have a house battery (LiFePo4) that is isolated from my truck battery. Bad news for me is that I mis-wired and blew my alternator fuse. I checked all the other fuses and none are blown. The alternator fuses are hard to find but I managed to find them on ebay.

 

Good, glad you found a replacement. Replacing it is kind of a pain in the butt, you have to get into the fusebox and undo a 10mm bolt. Have you done it before? If you have not, the threads above show the locations of the clips holding it together from the top, and give you a good view of the area where you'll need to work.

This should link to the post in question directly: https://www.tacomaworld.com/threads...ow-descent-into-madness.712981/#post-25452115

The bolt for that fuse is the one that is not touched/indicated, the top right one as pictured when seeing all three - the one that does not have a wire connected to it.

Here is a post detailing the specific procedure of changing that fuse: https://www.tacomaworld.com/threads...-box-battery-wire-replacement-upgrade.420450/

 

I managed to figure out to pull out the inner portion of the fuse/relay box by disconnection everything then releasing the clips. It makes it much easier to get to those retaining bolts. Your links with the pictures are very helpful too. I really can't do much else at this point until I receive the replacement alternator fuse. So far in my DIY adventure, I've learned a lot about what NOT to do.

 

220 amp from powerBastards
https://www.powerbastards.com/proddetail.asp?prod=11354-220-HD2-1
https://www.powerbastards.com/proddetail.asp?prod=PB-1001-01

 

Check out my video I just posted. Super simple, didn't need to mess with anything mentioned above