interference when rear window is on

[krazylegz]

since my cars been poorly the last few days i decided to in my Sony MEXBT3600 head unit as the standard was very poor on the radio, it seems to be better and the quality is a bit better than the standard but as soon as i put on the heated rear window it buzzes really bad

any ideas anyone?

[corsadonk]

Bad earth, check the ground wire for your system, and window de-mister.