big 3 with battery junction box?

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Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=95387
Printed Date: July 02, 2025 at 9:11 AM

Topic: big 3 with battery junction box?

Posted By: qwikrex
Subject: big 3 with battery junction box?
Date Posted: July 06, 2007 at 1:19 PM

Hello,

I'm preparing to do the "Big 3" on my 1999 Ford Explorer, and the wiring diagram shows that there is a "Battery Junction Box" between the battery and the alternator.

So, should I upgrade both runs of wire? Both from the alternator to the box, and from the box to the battery? Or just run one new wire from the alternator to the battery? Or perhaps something totally different?

Below is a picture of the wire diagram.

posted_image

Replies:

Posted By: DYohn
Date Posted: July 06, 2007 at 4:53 PM

Yes.

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Posted By: qwikrex
Date Posted: July 06, 2007 at 5:38 PM

Thanks DYohn,

I presume you mean yes to these questions?

"So, should I upgrade both runs of wire? Both from the alternator to the box, and from the box to the battery?"

And no to these?

"Or just run one new wire from the alternator to the battery? Or perhaps something totally different?"

Thanks! :-)

Posted By: aznboi3644
Date Posted: July 06, 2007 at 6:18 PM

What year is yours?? Mine is a 98 Explorer and I just ran a new wire straight from the alt to the battery....works perfectly

I also upgraded the wire from the factory alt wire fuse to the battery

Posted By: DYohn
Date Posted: July 06, 2007 at 6:32 PM

I actually meant "yes" in that you can do it either way. :)

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Posted By: qwikrex
Date Posted: July 06, 2007 at 8:48 PM

aznboi3644 wrote:

What year is yours?? Mine is a 98 Explorer and I just ran a new wire straight from the alt to the battery....works perfectly

I also upgraded the wire from the factory alt wire fuse to the battery

It's a 99, as stated in the original post. ;-)

Yeah, after actually looking at it in real-life, I see how it's supposed to go. It's basically just fusing the connection from the battery to the alternator and distribution box. Kinda strange!

I think I'll end up wiring it just like you did, with a direct wire from the alternator to the battery, and probably leave the stock wire from the battery to the distribution block.

Thanks!