Every time I remove the key from the ignition I find that the next time the key is inserted, Siemens CDR 500 radio asks me to re-enter the radio's code. It is a real PITA to do this each time I might want to listen to the radio but I am not sure where to start looking for the solution.

My first thought was that a fuse had blown but according to the radio's manual, the radio fuse is in slot 19. In fact, that slot was empty when I looked so I put a new 10amp in anyway but that made no difference.

I assume that when I withdraw the key that the radio thinks that the battery has been disconnected so asks for the code again next time I come to the car. Either there is faulty wire somewhere at the back of the radio or else there is another fuse somewhere in a circuit which is supposed to tickle the radio while the key is withdrawn to tell it that the battery is still there.

I have looked at all the fuses and their description but nothing jumps out so it is probably a wire.

Before I try pulling out the radio, anybody have any suggestions as to any other fuse which might be involved and which might need replacing? As far as I can see, everything else electrical in the car is working normally.