So I fitted a double din head unit in my 2008 Cooper S using this ISO connector with this:

Connects2 CT20BM03 Wiring Harness Adaptor ISO Loom For BMW


I connected the red wire to the cigarette lighter and now it turns on as expected when the ignition is on, however short term if I leave the car off for a few minutes, memory is fine. However after a few hours of it all being off, the stereo loses its memory. Has anyone experienced this? Some have said to swap the red and yellow pins about, another has said that the permanent live feed on the mini turns off after such time which is ok for original radio but I will need to wire in a new supply from fuse box for new install. Any thoughts?

Thanks

 

You do need to have a constant source of power to keep the memory alive in most cases. You can look for a head unit with - Zero Current Draw Memory (Retains Radio Preset Memory in case Vehicle Battery is Disconnected)

Not sure how easy it is to find them. Personally I'd be afraid to add a constant draw/drain from my battery.

 

I'm sure you got an installation folder with the harness. That should explain where you need to connect the red wire. My guess is constant 12V, either from the fuse box or directly from the battery. If you choose battery I would put a 2A fuse in place between the battery and the harness. If everything is connnected correctly the stereo should turn on and off with the ignition.

 

The harness comes with no paperwork just in a sealed bag with a label and their website has no instructions other than to say:

The harness works correctly as in it turns off and on with the ignition, thats with the red cable you see attached to the cigarette lighter 12v connection to get that signal from the car to switch on/off.

My issue is the memory loss when the car is left off for around an hour or so. I think the ISO connector is doing its job, looking at the harness that comes with the head unit that plugs into the ISO connector, that has a couple of switchable connections, 1-4 in the diagram below from Pioneer. I think this may be the issue. I need to look into it a bit further.

 

Just make sure "4" (yellow) has constant 12V, even with ignition off, - that should work.

 

Oh, and btw, I don't think you can tap the cigarette lighter for constant 12V. I think it shuts down 10 (or so) minutes after the key is removed.

 

I know the cigarette tap isnt for the constant 12v feed, its to give the headunit the signal to power on/off with the ingnition.