When I turn on my rear window demister, I get constant cracking through the FM stereo. Not so bad when I stop at the lights. When I turn off the demister, it goes away the radio is clear. All FM bands it seems. But AM radio is fine.

Anyone else get this?

I guess there could be a ground issue in the rear glass or a short?

Heater element & antenna are built into the rear glass. Check all connections especially the sticky pad at top centre of the screen. Give it a shove.

You don't have a metallic tint do you?

I dont think so, I never modded a thing. Previous owner I think kept it factory also.

Good!

Try isolating the rear demister if possible ie pull fuse or connecting plug & see whether the interference is still there.