it wont work unless head lights are on.  once headlights are tuned on the rear defrost will work.

any idea where to look?? any idea what may cause this??

help!

Oh.. that's simple... your power to the rear defrost has to come from the right fuse.. apparently your defrost is now on the line after the lightswitch.. whats not correct!

Take a good look at the 240z schematic and look at where the defrost is connected to the power..