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Need some help with upgraded battery (want back to stock)

1120 Views 7 Replies 3 Participants Last post by  perseus

2011 Mazda 3 S Grand Touring Hatchback 2.5L

Hey everyone

So this car was wired for subs prior to me buying it and I’m currently trying to get the battery back to stock

Couple questions about what I have going on here. First, is that fat wire coming from the negative terminal the ground? It looks like it’s just going to the engine bay with some custom mount. Second. What is the taped wire that’s near the fuse box? I vaguely remember the person I bought it from saying that’s the ground but then what’s the fat one? The taped one says kicker on it so it isn’t anything factory

In the trunk, I have two wires, one blue, one black that both look the same gauge. Haven’t followed them so not really sure how to handle them yet but I’m guessing one may be another ground for the amp?Have no clue what the other could be so let me know what you think

I attached a picture of the battery but let me know if you need any additional info

Thanks for the help!!
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I'll take a stab since I just installed a sub:

Usually, when installing an amp/sub, the only wire you would run to the battery is a large, red power cable that hooks up to only the POSITIVE side. In this case, my hunch is that that is the cut wire over the fuse box. That wire likely runs thru a hole in the firewall and powered the amp. Check under that black sheathing of the cut wire to see what color it is. In case you ever want to run a sub, you can leave the sheathed cut cable as is to use as a guide for your power cable to go thru the firewall. Or just reuse that one. From the inside of the car, you should see the cable(s) coming in near where the clutch pedal would normally enter the cabin.

Now as to what's happening on the negative terminal, more often you ground your amp/sub to a bolt somewhere INSIDE the car. There should be an existing ground bolt behind the rear, passenger-side seat. But in this case, they used the negative terminal on the engine battery instead. So the ground went negative terminal --> chassis using that Kicker adapter. I'm not sure about the 2011s, but if you look behind the rear seat on the frame of the car, you should be able to see where the factory wires are grounded (and where you should ground your amp if you decide to install one).

I'd remove the Kicker contraption, making sure you leave only the factory negative terminal hooked up and nothing else on that side. Then either leave or pull out that snipped, sheathed power cord from the inside of your car where the clutch pedal would be.

The first thing to do will be to unhook both the Kicker contraption as well as the car's power from the negative side. Once that is done, you can safely work on getting things back as close to stock as you want. You'll lose your settings after you hook the power back up.

Oh, and welcome to the forums!
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i'd keep the kicker battery terminal. there's nothing wrong with it. just move the ground to a better location
I think I see what you're saying. So basically he would keep the Kicker terminal and leave that small wire in the middle, which is the factory wire? Or is that just another ground wire? And then remove completely the wire in the larger casing that goes to the chassis. That one is unsafe anyways.
As an addendum, I think the blue wire in your trunk is probably that same cut wire by the fuse box under the hood. My hunch is that if you look under the loom of the cut wire, it'll be blue. It's normally red, and dd18 is correct that blue is usually a trigger wire. But you said it was the same gauge as the ground. Also, I just ordered a Kicker power kit, and their power cable is blue.

You probably have a LOC in there somewhere too. It's possible the only thing you'd need to do is connect the existing power under the hood, same for the existing power and ground in the trunk, find the LOC (or install one yourself), and then you have all the pieces to install a powered sub or amp and sub combo on your own.

ETA: A picture of the blue and black wires' endpoints in the trunk might be helpful.
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