I have a 1998 Renault Clio with standard radio cassette fitted which can do cd changing. I've bought and fitted a 2001 cd changer. I've modified the cable to fit the pins, but the head unit will not operate the cd. Is there a wire link I'm missing? What am i doing wrong? The changer powers up ok, but the head unit won't operate it.

Philip Sheen, November 2015