Hi, my headunit (Alpine CDE178BT) is draining my battery within a couple of days - but strangely it has only recently started doing this. I had someone confirm that the stereo was draining it, and after unplugging it altogether the battery has been fine.

I've tried switching the red / yellow wires around but the unit still powers on without ignition. How would I completely cut power to the headunit when turning ignition off? I would prefer not to as I'd lose my settings but it would be better than nothing!

Fiat coupes don't have a switched live to the stereo as standard which is a bit odd, but you can wire one from the cigarette lighter socket which is close by.

Agreed cigarette lighter is best for the switched live. There's a thread or two on here about which wire it is if you don't have a voltmeter.