I just picked up my 1989 XJS. When I start the car, the radio starts with "code" on the screen. I enter the security code from the owners manual and everything works great. When I turn off the car and restart it a minute later the radio has lost it's memory and I need to re-enter the code. It does it every time. Does anyone know where the constant power lead would be or if there's something else I should look at?

 

Could just be transposed switched and permanent 12V, thats a common mistake. Can you operate the radio regardless of key position? Other wise yes just missing permanent 12V.