Big Three Wiring Upgrade - 2nd Gen Tacoma - Writeup with pictures!

First install was important - This was a big three upgrade to pave the way for a switchpros and powertrays install.

Never really found a true write up for a big three upgrade, so I figure I could put one together. The install is straightforward but figured it would be good for those contemplating the mod.



The negative and positive cables were removed from the battery:





The cables will be completely extracted from the truck, therefore everything must go. Here we remove the ground off the fender:



Then I reached down and remove the wiring harness from a wiring clamp:



Save it for later:



Then I removed the mud guards in the fender well of the driver's side. This allowed some access to the wiring that runs to the starter.



See that ground there? - the one on the coil frame support right under the UCA, must be removed as well.





Once that is removed (not shown as removed in this picture), there will be a plastic cover that houses the wiring for the alternator and starter. Remove this cover, be patient. It is stubborn.



I removed the skid plate to look around and see if I needed to remove other stuff related to the wiring. Might be a good idea to remove it in case you need to reach in there for some oddball reason



Then the tedious work: Removing the wire loom and all the electrical tape holding the wiring together.





Work in progress:



Once all the tape and loom is removed there will be nothing but loose wiring, it is time to disconnect the starter wiring and ground. In this picture the starter wiring is wrapped in the foil looking insulation:



Remove starter plug and ground:



At this time, all the ground cables can be pulled out. Here is a comparison picture with the replacement upgrade:



See this black wire with blue line? This goes to the alternator FROM the inside of the fuse box.



It connects in here:



See this black wire? It comes from UNDER the fuse box. This wire will be routed INTO the fuse box and placed where the alternator cable is connected as shown in the above picture. We will get to that later.



Let's disconnect the alternator cable. I removed this bracket that is over the alternator for ease of access:



Once the alternator cable has been disconnected, disconnect the alternator cable from INSIDE the fuse box and pull it out.

At this point, the stock power cable and the fuse box to alternator cable can be completely removed. Here is a comparison picture with the upgrade wiring.

For reference, the longest red cable will run to the starter. The mid length red cable will run DIRECTLY to the alternator. The shorter cable will run into the INSIDE of the fuse box where the alternator cable was originally at. We will get to that soon, patience!



Red shorter cable running into the INSIDE of the fuse box:





Routed wiring to starter and alternator:



Reinstalled loom, taped wiring neatly and reinstalled clamp:







Not all the wiring fits in the wiring housing, so I routed the alternator wiring on the outside:



Reinstalled more loom:



Remember the wiring that comes from UNDER the fuse box? - run it INTO the fuse box using the same routing as the alternator cable that was removed earlier.



I removed a side cover and some plugs to allow ease of routing:



It is a TIGHT fit, but will work:



Reinstall plugs and side cover:



Connected positive and ground leads to battery:

 

Switchpros and powertray install will be part of another writeup thread.

 

Big thanks to @Denk for explaining what goes where via pictures here:

https://www.tacomaworld.com/threads...ig-3-plus-closed.391316/page-29#post-23206848

 

Well.

Done.

 

thanks biscuits!

 

What's the benefit of this and is there any data to support the benefit?

 

Lol I dont even know what he did.

 

Looks like he replaced some of the ground and 12v supply cables, which can be beneficial in some cases.

 

Great write-up.

 

Replaced w/ larger diameter (and presumable higher quality?) wiring. I believe the thought process is a larger diameter can support larger loads w/o voltage drop? I'm sure OP can elaborate or maybe @crashnburn80 can chime in.

 

Nice write up. Is that the Bamatoy big 3 upgrade? Looks familiar.

 

It sure is!

 

Yes, larger loads without voltage drop.

My main idea is to eventually add a winch setup.

 

But going back to what @GrundleJuice said, has anyone actually measured the before/after voltage drop, after...lets say, a winch install? My understanding of electrical components is the length of the run combined w/ the load requirement is what determines the need for a specific size wire. And I was never sold on the idea of increasing the "big 3" in a car b/c the runs are so short. I even have a box of wiring at home that I never installed on another car to complete this same project. I know in theory it sounds good, but I'd also be interested in some real numbers to justify the work. Heck, I'd even be interested in seeing numbers of stock setups, and minor electrical upgrades to things like lighting.
Not shitting on your writeup or install either btw. I think it's a good tuturial to have.

 

I agree! - A good writeup and test on voltage drops would be beneficial for all of us.

 

I didn't take it like that, we're all here to learn and build.

 

Ah, I see. Looks like there is already some extra electrical equipment that I do not recognize.

That would be nice to have the data, but if the changes (adding a winch, stereo/amp, etc) draw more current than the factory system then it's probably not a bad idea to do this. I very much doubt that Toyota designed any overhead into the electrical/charging system. Heck, can't even use a higher wattage headlight lamp without measurable voltage drop on the headlight harness assembly.

 

Winches are typically a game changer especially if grounding to the frame. My smittybilt 12K draws 342 amps at full power draw, that little 8 gauge grounding wire above running to the coil support tower was never designed for anything over 150 amps. I also put in a 250 amp alternator which requires upgrading over the originally designed 130 amp towing alternator. Add on additional solar charges and relocating cab batteries well that just makes the frame an even more appealing ground with less resistance than any 4/0 gauge wiring. However, if you never upgraded the grounding link from the frame back to the power source then it is all for naught.

 

Another solution in search of a problem