head unit wont work when ignition is on?!?

[nhop10]

please help. i have recently bought a mk3 golf gti 8v. the head unit worked in the car when i bought it, although it would not store any presets or anything, thought it was my electrics that were messed up as had a few other things not working properly. anyway i wanted to put another head unit in the car for the aux output. i just unplugged the old pioneer unit and put the newer one in. however the new one would only then work when the ignition is off, as soon as i turn the key it cuts out? i tried putting the old one back in and now that does the same - not working with the ignition or car on. no idea whats up so any ideas would be a great help..

[jv]

Generally messed up permanent live/ignition live wiring I guess. Take it to an auto electrics place if you are not confident messing about with it yourself

[JC]

there abouts in the Oxon are you ?

[nhop10]

near henley, between oxford and reading. tried having a look earlier but couldnt work it all out. doesnt male sense to me as it did work with the car on before i took the unit out and put it back in. will probably take it to someone who can have a proper look