is it a completely different model headunit to the original? if so, what model?
what happens if you manually turn the stereo off when you LEAVE the car. THEN when you return, and start the car...does it come on automatically?!
generally, if you manually turn it off when you leave, it should not come on when you return. but if it's on when you turn the key off (and it switches off automatically), it will come back on when you start the car. that is normal.
