Shiny, after watching your 155 thread on the ICE build you did over on the .org I have come to think there is nothing you don't know about stereos...
Car audio basics are just that - pretty basic. Except most people are disinterested and see no relevance, and are never inclined to learn. But once you get started, and do it yourself, you learn fast. Of course, as a passionate hobby of mine, I am motivated to digest and learn, and take it all onboard! If I can help others, all good.
Hi guys thanks for getting back to me. I have only had the car 3 months although its a 2002 reg so not exactley sure if there was electrical work done on the car. There is no phone kit or any other accessory fitted. Its I suppose a prefacelift car. The stereo fitted is a Blaupunkt Modena CD51 which must have been retro fitted. It works without the key in ignition and when ignition is switched to MAR but when key is turned to say position 2 or when the car is running the sound switches off. Speakers are original and there is no amp etc. Thanks lads.
As Lacken156 eluded to, that is an aftermarket headunit. So there's every chance it's not wired properly. Or, a fuse is blown, relating to power supply when the engine is running.
If it's a prefacelift dash, there are 2 main power supply wires, in addition to the ignition wire.
Presuming you're not going to troubleshoot the wiring yourself, take it to a specialist ICE store to check. If you're going to DIY, remove the headunit, and use a multimeter to check the wiring.
For reference, this is the wiring schematic for the PREFACELIFT dash 156s. Note the 'constant' +12V feeds in positions A4 and A7, and 'switched' ignition/ACCessories feed at A3. This setup is unconventional, but must obviously be observed and rewired accordingly to suit a new headunit.