This time of the year, driving into a parking garage tends to fog up the windows on the outside. I usually activate the rear window (and wing mirror) defroster well in advance to counter this. In doing so, I've come to notice that the apparent defroster wires on the upper portion of the rear window are slacking off:



My immediate thought was that the defroster lines must be damaged, as I had that problem on a prior car. However, while the functioning wires run the entire width of the window, connecting to thicker conductive areas on the sides, these upper portion wires do not. Rather, they're connected to one another by a vertical wire, which then goes to the black portion on the top of the rear window. That suggests this is a separate defroster element.

So...why does the upper element not do anything? Blown fuse? Working as intended? Activated automatically when His Lexusness so desires?

 

I think that's the radio antenna.

 

You're probably right. Parts catalogue shows some kind of an antenna module near the 3rd brake light, close to where those upper "defroster" lines originate from. Now that I think, I used to have a Jaguar X-Type on which FM reception would go to crap whenever the rear window defroster was on. Perhaps it used the wires as an antenna or something, while Lexus has separated them to avoid interference.

 

Correct, those aren't defroster lines its the radio antenna.