Hi all, I`ve got 2 CDR 500 radio`s for my M reg Astra, and have a question. The one that was fitted by a friend for me works perfectly. The second one, which I was testing before selling to a friend, will only display "CODE, "PANEL" and the PIN number as you enter it, it won`t show any CD or radio channel information. I have swapped bewteen these radios a few times and the old one works perfectly, the new one doesn`t. Any suggestiosn as to what it could be? Thanks in advance for your help!