Hi trying to put a sony cdx-c580r (quite old but working!) cd head unit in to a L reg corsa. The problem I'am having is that i cannot get any display on the head unit, the radio works and the cd player. I have pluged in the two sony cables into the 3 corsa ports, i know that one of the corsa ports is for putting the display on the cars dash but i dont want this. I'm wondering if the cars dash display is stopping the display on my sony head unit. Has anyone got any idea what the problem could be?