How can I stop my radio cutting out?

I recently bought a Peugeot van with a Blaupunkt radio in it. When switching it on the code was requested so I released the radio from the dash, found a sticker with 0782 on it. Tried this number as the code. The radio came on, kept making a bleeping sound (like interference - engine not running) while it was playing and after 5 minutes cut out and requested the code again. It does this everytime I try it. Presumably the code is the correct one or it wouldn't play at all would it? Anybody have any ideas? (hopefully other than buy another radio!!) Thanks