Battery Cable Replacement

Hello everyone,

I recently inherited my 2003 Toyota Tacoma V6 Prerunner Double Cab. The truck itself still runs great with 300,000+ miles. I'm somewhat mechanically inclined as I can handle basic maintenance but the electrical wiring portion almost goes over my head. Even then, I would still like to learn how to do it.

What I want to do.

• I need to replace the battery cable because the cable ends along with the terminal connectors because they are corroded. The cable ends are frayed and the brass connector is now a bluish gray. I figured since I'm in there I would also swap out the ground cables along with the connectors for the alternator and solenoid. I plan to buy some 1/0 AWG for the new cables.

What I know.

• Positive battery cable connects to the positive terminal, the starter and the alternator.
  
• Negative battery cable connects negative terminal to engine and frame grounds. (Correct me or add on if I'm missing anything.)

What I don't know.

• I'm not sure if the additional cables with the connectors to the alternator are spliced into the primary cables too or if they are dedicated cables connecting somewhere I am unaware of. If they are spliced in, which ones are they spliced into and why?
  
• I don't know the connector heads and I've been look at the wiring diagrams but can make heads over tails.

Any help would be appreciated. I am attempting to complete the big 3 upgrade for now. And then complete a headlight wiring harness and light bulb upgrade to the Osram Nightbreaker 200 bulbs afterwards.

Thank you.

 

Everything will have a dedicated cable.

For 12V+ from the battery you just have the cable to the fuse box and the cable to the starter.
From the fuse box it branches out from there, but each cable will be fused from the fuse box.

There might be cables that are bundled together in the wiring loom, but not spliced together. There would be a noted splice in the wiring diagram if that was the case.

 

OP you have a crimper to crimp on the lugs for your new cables. You do have the lugs?

What kind of battery terminals do you plan to use?

Make sure to get the correct cable for automotive use.

I use welding cable scrap pieces for the cables I make.

Remember the positive lead to the fuse block is bolted fast to the underside of the fuse block.

 

I figured out the connector wire on the starter. It's the signal wire to the solenoid on the starter. It seems to be bundled with the main positive wire like you said but I don't see where it ends on the bundle when I trace the wiring loom back. Same issue with the alternator. I can't seem to trace where the exciter wire goes to in the wiring loom. My understanding is both connect to the ignition switch through the fuse box.

I plan on picking up crimpers and lugs. Any recommendations that won't break the bank? I hear Klein is very popular.

I keep seeing everyone say military terminals because it makes future add-ons easy, so I might just grab that since I have grand plans for my white taco.

Would 1/0 Copper AWG not be universal? I'm assuming insulation differs based on uses since you asked.

And thank you for the heads up about the positive lead being bolted to the underside of the fuse box. My positive lead has a white insulated copper cable, besides the main cable, that leads to the underside of the fuse box but I couldn't see where it went from the top of the fuse box. I also noticed another another cable attached to the top of the fuse box from the cable bundle, so it's throwing me off.

 

You know you can buy them pre-made, which you might be better off doing. Even you local autoparts chain store should have most of your pre made cables.
And there are plenty of places online.
And yes Klein tools will break the bank. Stick with Harbor freight if you are trying to not break the bank.

https://forum.ih8mud.com/threads/first-gen-tacoma-battery-cable-kit.1189564/

Good Luck

 

The wire on the top might be going to the alternator.

My crimper was $300.00 about 10 years ago . Then I crimped many lugs on cables for work.

1/0 copper is the size not the type of cable . 1/0 battery cable is about $7.50 a foot right now,

I use all Marine battery terminals.

Pre made cables might be a option to checkout.

 

I would clean everything up and do some voltage drop testing before I committed to replacing everything.

 

Be wary of some of the premade heavy gauge cables for sale online. One heavy gauge "Big 3" set I looked at had a great price; they almost had me convinced to buy them. But reading the fine print, the cables were made of heavy gauge copper clad ALUMINUM (CCA) wire. The same problem applied to some heavy gauge jumper cables for sale online. .02

 

I agree with this ...park in street, brush with soft wire brush (or old toothbrush will even work) sprinkle with baking powder, then splash with vinegar, gently rinse with water, repeat until clean. THen you just need the correct bolt for your battery terminal to tighten it. Wear gloves, while battery acid doesn't eat through you skin immediately like Xenomorph Blood, it will definitely will cause irritation that doesn't go away.

 

Wasn't there a member here making some nice upgrade drop in replacement cables? I'd trust those more than picking something up at a parts store.

 

I was just thinking about doing this as well, I had settled on this kit, unless anyone has an objections.
https://jeepcables.com/toyota-tacoma-big-7-complete-kit-gen-1-1995-2004/

 

Crazy prices !!

I would go with the 1/0 cable rather then the 2 gauge. If your upgrading!

 

Second the welding cable recommendation. As for crimpers, I went with this one and have not had any issues whatsoever. Use a mini-sledge and good to go.
Forney 57637 Lug Crimping Tool

$20 Forney 57637 Lug Crimping Tool, Blue

https://www.amazon.com/dp/B003X51S00

 

I took one of those built a frame installed a 4 ton hydraulic jack works good for $20.00 the other parts were odds and ends laying around.

took some experimenting to not over crimp . Was great for making cables it sits around some place.

 

I'd suggest, that for an average member here, $145 is not that crazy... I like to buy tools and have tools on hand, but even I wouldn't buy crimpers and build a frame for a 4 ton jack just to make some new battery cables one time.

 

If you knew the thousands of dollars I have invested in special tools for one job you would roll on the floor laughing.

I crimped many lugs with that cute little tool.

For one set I would buy pre made cables and never give it a thought.

 

Thats kinda where I'm at, I am all for having specialty tools on hand, but with this its a one and done thing and even if it costs more premade saves me a lot of headache and time.

 

After reading through everyone's feedback I'm going to pick up the premade cables. That still leaves me with the switch connectors and wires for the alternator and starter. I might just leave those be for now.

I'll also conduct a voltage drop test before committing.

 

Well, what did you do OP?

 

They have not been here since December 2022.

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