I have a 54 reg MG ZS 120+ which has an annoying fault. When I listen to the radio the reception is very poor and there is a constant crackle in the background. I have tried two identical head units and the problem occurs with both. This only happens when the engine is running, when it is off the reception is fine. Also the head unit worked brilliantly in my old car, does anyone have any idea what is causing this as it is driving me mad?!