when the defrost is on the radio gets static.. I know this has been written before but - what causes this and what is the fix?

 

The antenna is in the back window along with defroster wires of course, a common occurrence was that the defroster had some broken elements along with the interference.
Do you have broken elements, does the defroster work at all? Maybe the wires/elements are shorting out somehow.
A poor ground was also suggested.
This the area in the 2004 Service Manual that touches on these two items.
8A - 24 AUDIO - SERVICE INFORMATION

 

I acquired radio static/interference after installing the LED license plate lights. Of course,it happens only when I turn the lights on. It did this with both the OEM head unit, and my new quality aftermarket head unit. I don't know if these two issues are related or not ; but I'd sure like to know the cause and the fix; (and for me anyway) without having to go back to the incandescent. As 180 has mentioned; the common denominator is the general location of the rear defroster element, the license plate lights, and the antennae. In my case, I don't believe I have any shorts. Another member has also suggested that I open up the back hatch panels and separate any common ground back there.

 

Same thing here when I replaced my license plate lights with the new LED sealed units
I have read a few others have experienced this problem too without explaination

 

Not quite the same thing, but I once thought it would be a good idea to replace the 2 bulbs in the garage door opener with LED's. NOT A GOOD IDEA !
As long a the lights are on, the RF unit is unresponsive.
This means you have to wait a long time before you can close the door after exiting, also same when driving in, although the wall switch fixes that.