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I had to have my 2002 Mustang GT towed to a repair shop, this past Saturday morning, because it wouldn't start. It cranks over (VERY strongly, LOL, thanks to the Optima Yellowtop battery I bought for it, the night before!), but it won't start. The shop I had it towed to diagnosed the problem today as the fuel pump isn't operating, because it's not getting any power through the battery junction box (or, power distribution box, or whatever it's called) - this is the box with the fuses/mega fuses/relays, that's mounted right next to the battery. I suspected this might be the issue, and I'll explain why.

I drove my wife to her job on Saturday morning, and I had no problem with the car. When I got back home, I was trying to get that nut off of the stud on the battery junction box that the cable from the alternator connects to. The reason I was doing that is because when I bought the car almost four years ago, I had to right away replace both the battery and the alternator, because the car wouldn't start the day I brought it home. I bought a Motorcraft battery, and an higher-output alternator, rated at 250 amps, I believe (it was actually less money than some of the rebuilt, standard-output alternators that were available for my car, and the dealer I bought the car from compensated me partially for the parts costs). Due to the higher output, it was recommended to install a thicker-gauge wire, so I bought an upgraded wire from American Muscle. However, I've NEVER, in almost four years of occasionally trying, been able to loosen that nut; I've only succeeded in distorting the box, because I'm assuming the copper plate inside was bending (mine looks like the one in the picture I've attached to this post). The nut seems to be "welded" to that stud; I'm assuming this is due to a combination of electrical current flowing through it; age, and underhood heat. When I was trying to loosen it this past weekend (yes, I've always sprayed penetrating oil on it, before trying to loosen it), the whole stud felt almost "loose", as if it was broken (or, nearly broken) off of that copper plate.

As a stopgap measure, I simply attached that upgraded alternator wire directly to the positive terminal on the battery (leaving the stock alternator cable in place, obviously, because I can't remove that nut), but I'm not sure that I'm getting the full benefit of the higher-output alternator I have, and I'm not sure it's necessarily good for my battery. As I spent $231 on that Optima battery, that's now become an important consideration for me, again - that's why I was messing around with it again, on Saturday. Besides it not starting (it actually started after I was messing with that nut/stud, but was supporting, as if it was running out of fuel, which it was), I have had other issues because of it, including the car overheating once, due to the electric cooling fan not running (the fan wasn't bad; when I squeezed the two halves of the battery junction box together with my hands, it started running).

So, anyway, if I understand correctly, that battery junction box only came as part of the whole underhood wire harness. The part number for that harness for my car, as given to me by a Ford dealer today, was 2R3Z-14290-AA (that number only fits certain 2001 & 2002 GTs, depending on build date, and there's two different harnesses, depending on if you have a Mach 460 or a Mach 1000 stereo system) and, of course, it's long since obsolete. I found a couple of harnesses on eBay, and I'm waiting for responses from the sellers as to whether or not they can provide me with the Ford part number, or the exact kind of Mustang it came out of.

Here are my questions, if anyone can answer them:

1. Is that battery junction box the same across all the different wire harnesses? Can I just go to a junkyard and get one off of a Mustang that's a 2002 (or, thereabout), and simply remove the wires from it, and then substitute it for my damaged one, and simply plug my existing wire harness into it (taking care, of course, to make sure each individual wire is plugged into the appropriate slot)?

2. How does that box come apart? I took mine off of the bracket it's mounted to, and was able to tip it forward (towards the engine), so that I could see (sort of) the underside of it, and the black plastic cover on the bottom of it the whole, thick wire harness goes through and up into the box was loose, but it looked like there was a red plastic piece that the wires ran up into, and I couldn't figure out how to dislodge/remove it. I couldn't really position it into an optimal position for what I was trying to do, as I could only stretch the harness so far, and didn't want to inadvertantly pull any wires out of it. Anyone have any pictures on how to take it apart?

3. Anyone have the correct harness, or the battery junction box, if that part is the same regardless of the harness part number, that I could buy, or know someone who might have it?

Thanks!

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If at all possible, I would pull the junction box off and inspect everything before spending money on something that may not work. You could have a bad or loose connection that can be repaired.

A salvage yard part may work. However, there is always the chance of having the same, or a worse issue if the problem really is in the fuse / relay box.

If you enjoy fabricating now could be a great time to build a custom enclosure.

Also, these cars are picky about voltages. I have learned that small, common changes in the alternator or other components have the ability to confuse the entire car's electrical system.

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If at all possible, I would pull the junction box off and inspect everything before spending money on something that may not work. You could have a bad or loose connection that can be repaired.

A salvage yard part may work. However, there is always the chance of having the same, or a worse issue if the problem really is in the fuse / relay box.

If you enjoy fabricating now could be a great time to build a custom enclosure.

Also, these cars are picky about voltages. I have learned that small, common changes in the alternator or other components have the ability to confuse the entire car's electrical system.

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That's my entire problem - bad connections, due to the box being distorted from my attempts to get that nut loose from the stud where the alternator cable attaches to the battery junction box.

If you look at that picture I attached (that's not my car; I got that off of the Internet), where the red circle is, there's a significant gap on mine, between the two halves, upper & lower. That's because, I believe, the copper plate inside is bent, from my attempts to loosen the nut, and that's caused problems, due to connections not being made properly (such as my car overheating when I was running the A/C, due to the electric radiator fan not running). I put two large wire ties around the upper and lower halves a few weeks ago, to pull the two halves together tightly, and things were OK for a while - until I tried loosening the nut, on Saturday. Now, the car won't start, because the fuel pump isn't getting electrical power from/through the battery junction box. The repair shop told me several different wires are also becoming dislodged from their connections within that junction box (they said they removed it from it's mounting bracket, to examine it more closelyl.

Also, as I previously stated, when I put the socket & ratchet on the nut on Saturday, it felt "loose" as I was trying to loosen it; the two cables that are attached to the stud were moving to the left or the right, depending on whether or not I was attempting to loosen or tighten it (I was NOT applying very much pressure, as I was worried about really screwing it up, which I obviously did). I'm afraid that stud and the copper part it's attached to are separating/breaking off from the rest of the copper plate that they're attached to.

I need to obtain one of those battery junction boxes off of a Mustang in a U-Pull-It junkyard, so I can take it apart and see exactly how it's assembled, and whether or not it's identical to the one in my car - I'm betting it is (I'm betting that just the actual wire harness itself is different, between model years; options, and part numbers). I was just hoping someone on here would know, and could answer that question for me.

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I can't give you any specific answers to your questions regarding the under hood power distribution box, as I have not had to mess with it too much.
As far as I know, the only difference in the electrical system between the different cars, is the stereo system, and the Cobra/Mach/Bullitt cars have a higher amperage alternator. You are probably correct in your assumption that the boxes are the same on all of the New Edge cars.
Most of the large automotive salvage yards have software that will list all of the different vehicles which use the same part number that you are looking for. Bring your part number, and VIN number when you go. Also, the "pick and pull' salvage yards are a great place to learn how to remove parts from a specific vehicle without risking damage to your own vehicle/ parts.
Another possible source is Craigslist. Someone nearby you may be parting out a wrecked New Edge.

Since a new one is no longer available, you are just going to have to do a little sleuthing, but I'm sure that you will be able to get this repaired.
Hopefully, in the meantime, you have an alternate means of conveyance until your Mustang is fixed.
 
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