[Closed] Calling car audioists or electronic savvy people

Looks like a ground/earth wire or at least the terminal gives me that impression, does it connect to the chassis of the Amp?

Looks like an earth. Should be grounded to the car body work with an unpainted bolt or screw. You can use any nearby existing bolt/screw just make sure it's clean and remove the paint around the hole in the body work to get a good contact. If it doesn't screw into metal then look for one than does.

Got a multimeter? Might pay to check to see if there is 12v present on the wire before you connect it to earth. It could be anything.

....may even be the switched 12v from the headunit that turns the amp on...

If it's 12v+ with that connector then someone is a very bad installer, anything other that an earth then shot the person who wired it, you'll be doing everyone a favour 😉

Edit, unless it goes to the amp end, but hard to tell from your pic.

Ok so connected it all up and is working fine without connecting the above wire. Dunno what the wire is so just left it unconnected.

It's an earth strap. Strap it to earth.

What is the other end connected to ?
You should check with a multimeter or a lamp before grounding it....

Has that connector even been crimped ?

You might not need it unless you start getting interference when you put your windscreen wipers on or some sort of interference in sympathy with engine revs. Or it could be a switching live intended to be connected to a switched live? Does the system work when the ignition is off?

Everyone is assuming that the person that put it there knew what they were doing. Dangerous.

Find out what the other end of the wire is attached to before you connect it to anything.

You might not need it unless you start getting interference when you put your windscreen wipers on or some sort of interference in sympathy with engine revs. Or it could be a switching live intended to be connected to a switched live? Does the system work when the ignition is off?

Only with ignition on. All working ok so maybe it was nothing.

Everyone is assuming that the person that put it there knew what they were doing. Dangerous.

Find out what the other end of the wire is attached to before you connect it to anything.

Seconded, but it does look like an earth. Though I'd expect it to be at least crimped green for clarity.

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Assuming you are using an amp wiring kit/original wires with amp, the colour black would mean it is an earth wire.

If you think you have a wire left over, I would check through all your ICE wiring to make sure it is correct.

While you're all here, my alpine stereo doesn't work without the ignition on, any ideas what or if I've missed if anything? There weren't (that I can remember) any spare wires.