I've just got a new Brodit iPhone charger cradle. The company that fitted the stereo CAN bus adapter had wired the previous charger using the switched 12V coming out of the CAN bus adapter so that's what I did with the new one. The new charger seems to draw more current, on its own it only charges for few seconds then stops. If the radio's on that cuts out too. With no phone in the cradle the radio's fine. Could I wire the phone charger in to the permanent 12V? Even if I left the phone in the car some kind passer by would remove it for me before it flattened the battery - I assume the charger won't draw any significant current with no phone in the holder.
I managed to hook up a multimeter in series with the charger and it doesn't appear to draw any significant current with no phone connected so I connected up to the permanent 12V and haven;t had any problem yet. The big test will be after something like a holiday