Headunit will turn on when ignition is off. But turns off when ignitions on.

[jakeria]

I have a 1992 nova saloon. Running standard speakers in the front in the dashboard and some JBL's in the back, I recently changed headunit from an aftermarket JVC, to an alpine. with 4x45w outputs. I wired in the new harness and plugged in the radio. It worked fine, or so I thought until I turned the car on and the radio wont turn on at all whilst the ignition is on, I've also noticed that when I turn the volume upto about 14 (out of 40) the radio resets itself. I've replugged in the original headunit I had and that does the same now. So not really sure If I've wired it wrong. I know all the speaker cables are wired up right as all the speakers play music at low volume when the ignition is off.
I've looked at the red and yellow cables in the back, both the red and the yellow from the back of the headunit are wired into the red cable from loom, is this the constant 12v supply?
(the only yellow cables I have from the loom are for the front left speaker, yellow and a yellow/brown) Which I found odd, thought there should be a yellow cable that is switched current? Whilst probing what could be wrong I checked the grounds and they're fine.
I have made sure the fuses are fine, I've got a 10amp in the main fuse box which was in there when I bought the car, and a 10amp in the back of the headunit.
I have noticed that when I turn on the radio before starting the car, if i turn on the ignition so the electrics come on the radio goes off, I can hear a click from the engine bay. This is a small relay which has something to do with the car running, as when I took it out the car wouldnt start. Dont think this has anything to do with why the radio wont work.
I have a quite thick brown cable not connected to anything from the car loom behind the radio - dont know what this is for. And another blue/gray cable. I dont have a volt meter so its a bit difficult to check the power outputs haha. Anyone got any ideas?

[BigDave1979]

It sounds like you've got your wires mixed up, and it sounds like you may have connected the radio earth to the ignition live. Check your wiring.

On the vauxhall loom:

Red is Battery +
Black is ignition +
Brown is earth

I'm guessing your radio is working when the ignition is off because it's earthing via the aerial, but it's not a good earth hence it cuts when you turn it up!

The blue/grey cable - could this be grey/green? This would be the display illumination. Always best to check it if you can borrow a meter, or make up a tester with a couple of bits of wire and a bulb!

There is a sticky at the top of this section that has all the radio connections.

You may have blown a fuse in the process as well, so check your fuses!

[F124nny]

See if your speeker are earthing out I had this when my door speaker was earthing out

[TINTIN]

Have you still got the original connector plug in teh car or has that long since been chopped?

The ISO connector from the rear of the head unit should have a red wire and a yellow wire connected to it from plug to plug. These need to be switched over so red to yellow and yellow to red. That should stop you having to retune your radio every time.

If you can it might pay to take a pic of your wires and post it up for people to take a look as it sounds to me as though your not 100% confidant in what your doing and could cause your self more harm than good.

[BigDave1979]

Tell us what model Alpine headunit you have as well. I might be able to find the wiring diagram for it.

[jakeria]

Awesome info guys =) Sorted it, yeah I had the earth and the ignititon + the wrong way around haha, I just joined the cables because they were the same colour haha.