Alternator Fuse and Fuse Box-Battery Wire Replacement/Upgrade

Here are some photos and tips to removing the fuse and replacing the fuse box-battery wire. I have a V6 auto 07 Taco; your box may differ but similar principles should apply.

I took apart the fuse box to replace the fuse box-battery wire and took out the fuse to see how it's done in case I ever have to replace it. Didn't find a how-to; so I posted this for future reference. I had wanted to replace the OEM fuse with a 200 amp fuse but I couldn't find one (prepping for a future alternator upgrade). The one in my truck appears to be the max they make, a 140 amp fuse. I'll be running a fused jump wire - alt to relay to battery once I get my 2nd battery installed.

1. Remove battery; remove fuse box cover; open wire harness connectors on fender wall - the two closest to fuse box. Also consider clipping the zip tie on bottom of fuse box. Both will give you more leeway to install the fuse box tray later on.

2. Remove nut (12mm) holding alternator-fuse box wire, and disconnect the three harnesses.

3. Use pliers to pull out the small plastic cover covering the cable and harness wiring. Push wiring out of the way.


4. Use small screwdrivers (or awls or single strand wiring) to hold open the six tabs (red arrows) that clip the fuse box tray/panel to the fuse box. Use pliers to gently pull up the tray (at blue arrows). It will slide on grooves straight up; don't pull on the tray until the tray clears the grooves or you may damage the thin grooves. I found it easiest to work your way from left to right.


5. Remove bolt holding one of two fuse hold down bolts (M6 bolt with 10mm head). Lower bolt/wire goes to battery. Your wire will be a 5 gauge black wire; I upgraded mine to 2 gauge: 14.5 inches long; 6mm (1/4") lug on fuse box end; 8 or 10 mm (5/16" or 3/8" depending on your terminals) on the battery end.


6. Remove this wire harness 'socket'. It has four tabs and is a bit tricky to pull out. It will take some wiggling as it is connected to another socket. Tabs are not inside the three holes; they are low and outside the three holes.


Harness socket removed. You can now access the other fuse hold down bolt. That's the AC fuse bolt next door.


7. Voila. Now, put it all back together!


8. You may have to enlarge the hole a bit where alt-battery wire exits the fuse box to fit the larger gauge wire. I went a bit overboard. Use new zip tie to hold wire in place.



Here is a side comparison of the OEM fuse box to battery wire and replacement upgrade wire.



Here is a cross section of the wires, comparing 2 gauge, 4 gauge, and the OEM 5 gauge. I call it 5 gauge because it measures 4.8mm; close to 4 gauge (5.2mm) - call it 4.5 gauge.



My thoughts on replacing the fuse box-battery wire, and I can be completely wrong on this: The theoretical amperage limit of a 5 gauge wire is about 90 amps. The fuse is 140 amps. It's possible, then, that the 5 gauge wire will heat up and possibly catch on fire before the fuse blows. Those of you without the 130 amp alternator will not have to worry as much. I'd rather play it safe. The alternator to fuse box wire is 4 gauge; so, this short fuse box to battery wire is the weak link - not any more ...

 

Nice work, very thorough write up.

 

Good job, but I think your worries are unfounded.

The factory copper appears to be the same cross section of the wire ( not the insulation ) as the 4 gauge wire in your picture. Barring a loose connection I can't see this wire burning up or catching fire....

 

Huh... I may do this tomorrow just for some extra peace of mind. I have tons of 1/0 guage cabling leftover from spare projects. This should work out just fine.

 

Wires looks similar but I measured a difference with digital calipers: 4.8mm for OEM and 5.2mm for the 4 gauge. If I wasn't doing some other wire upgrades for preparation of a 2nd battery install and future alternator upgrade, I would not have noticed the different gauge wires used.

 

Caught a mistake in #5, bolt is M6, not 10mm. The head uses 10mm socket, is what I was trying to say. Fixed.

 

Just did this today! Thanks for the write up! It was perfectly executed and easy to understand.

 

My wire is also too short for my Northstar 31m so thanks for the write up. Surprisingly hard to get a replacement wire. My soldering skills sucks and I don't own a good crimper so thank goodness for online!

 

@HandOfGod A battery shop should be able to customize a battery cable for you. They have connectors also and I'm sure they'll crimp whatever you take to them.

As an example, here is local battery shop in my area that offers customized cables.
https://deepcyclebatterystore.com/battery-cable-for-sale/

 

I just ended up getting the wire at Amazon. I couldn't find it in black but no big deal. I will look into local battery shops for the other wires. Thanks again for the write up.

Camco 47480 Red 3/8" Stud 18" Long 2-Gauge Marine Battery Cable and Tinned Lug Assembly

https://www.amazon.com/gp/product/B00JGJGLMM/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

 

For anyone wanting to do this yourself, you can get a hydraulic crimper on Amazon for $30-$40

https://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias=aps&field-keywords=hydraulic+crimper

And you can use a cutter like this to cut the thick wire

$13 Cable Cutter Heavy Duty 10" Tube Wire Pliers Hand Tool Yellow

https://www.amazon.com/Cable-Cutter...=1503930649&sr=8-4&keywords=thick+wire+cutter

 

Chuy:
Thank you for the right up! Was most helpful.

 

@arwinnnsd You are welcome. Did you lengthen the battery cable? I would like to add an estimate length for those with center terminal batteries, ie NorthStar batteries.

 

Yeah, I went with a 2 gauge x 18"; just installed it yesterday, seems a bit long. But I'm getting my x2power (similar to the northstar) group 31 battery tomorrow and hope to install it Friday, so we'll see how that works out.

 

I used zipties instead of wire to hold the tabs in place, found the zipties easier to work with.

 

Here is the Camco 18” 2 gauge wire from Amazon compared to the stock wire.

 

Thanks for the write up! Blew my ALT fuse yesterday and need to replace. This was the only write up I could find on this without actually breaking the fuse box. Much appreciated!

Going to tackle this once this snow storm passes.

 

Just a heads up to anybody only needing to replace the ALT fuse and not doing the cable upgrade. I just had to lift the fuse box up on the left side and I was able to get to the ALT fuse bolts. I also didn't need to disconnect the two wiring harnesses going to the fuse box from the side of the engine bay.

Took me about 20 mins to do the ALT Fuse. Cheers!

 

@CODOTUS The fuse has two bolts. I can you removing the one facing outside the box, but how did you access the bolt facing the inside?

 

Took the female plug out in your 4th image. Just raised the left side of the fuse box up and got the 2nd bolt.