If the top line of rear window is the antenna,it doesn't defrost?

Yeah, I'd think it would have lines, too, unless some new way of doing it that I'm not aware of. Maybe the rear window was replaced with a window without the defrost option. There should be a small two wire connector coming out of the back shelf near lower driver's side of rear window. That would be the defrost connector to the window lines (that aren't there,lol).
Well, good luck with that! I think there are aftermarket kits for rear window defrost, though.

Between the rear passenger window and the back window is a junction where rear defrost wiring and radio antenna connect. Rear defrost wiring becomes loose and burns this unit out. when looking for replacement at salvage yard everyone of them I found had burned up. Lots of La Sabres w/o working rear defrost. I made solid connections for defroster, and added an antennae, not much point in repeating a system that will fail again.

the vertical lines running between your rear defroster line on your rear window are the antenna

check that the antenna cable is still plugged into the back of the radio and plugged into the bottom of the antenna at the finder to check radio end insert 4 large paper clips into the square holes in the front corners of the stereo this disengages the lock mechanisms slide the radio out and check the connections if electrical antenna check the fuse on the back of the radio that it isn't blown if so replace. loosen the inner fender panel and see if cable still connected to antenna #2 check the fuse for the rear defroster its probably blown if so replace and check for any grounded out hot wires also check the connections at each end of the rear window sometimes they become corroded or unglued from the window, if any of the fine lines that cross the window have been scratched or removed partially this will also render the defroster inoperable

Materials:

• Warm sunny day
• Tarp
• Large plastic garbage bag
• Undiluted Ammonia
• Windex (a glass cleaner)
• Paper towels
• Fine steel wool
• Razor blades

Tips:
The difficult thing about removing tint is that most film is constructed of two layers of tinted polyester. When you try to peel the film off the glass, the top layer will usually pull right off leaving the second layer behind. This second layer will not peel off, it will just flake and tear like a price tag.

Step 1:
To over come separation between layers you must soften the adhesive so that both layers peel at the same time. This is very important, if you peel the just the top layer, you may as well just use razor blades as there is no way to peel the second layer off without picking at it for a few hours. You MUST try to peel both layers at once.
NOTE:
You are more than likely to damage one or more of your defroster lines, when this happens, the cut line will not work anymore. Some cars have radio antennas mounted alongside the defrosters made of the same material. If you damage these, your radio antenna will not work! Be careful! Taking it to a tint shop to be done greatly increases the odds of saving the lines, but even a tint shop can not promise to save your lines, sometimes the film is just to far gone.

not a defroster

The top part is the antenna. If the whole thing doesn't work ck this out.

My defroster quit too. I found a wire burned in the connector that is found under the fuse box that is located inside the car on the passenger side kick panel.
You have to remove the entire kick panel to access the large white connector not just the fuse door. The panel just unsnaps as you lift up and out. Start from the panel seam beside the passenger seat and lift up and back. You'll also have to unsnap the carpet there too.
You'll see the white connector that has a lot of wires on it. If you'll unsnap the connector you'll see the burned wire. It will be thicker than the others and purple. Just cut the purple wire on both sides of the connector and splice them together with a piece of wire the same gauge and it will work fine.

your problem is in the window..........if you are getting 12v to the wires that connect to the window the lines in the window must have a break in them ............. they must conduct the dc volts to complete the circut, the lines heat form the voltage running through them thus ridding your window of fog and ice
hope this helps...........thanks for choosing FIX YA!

I found this on another site... it seems like a credible post so I thought I'd share... I'm going to check it out next weekend.

"Just an FYI. The rear defroster issue is due to a bad Antenna Buffer Module / Antenna Module. The power to the rear defogger goes through a module that separates the antenna amplifier signal from the 12 volt power to the defogger. The defogger elements also act as the antenna. The module is behind the rear pillar right behind the rear passenger door. The inside plastic has to be gently pulled off, the seat needs to be folded down to get the lower part of the trim off. One screw at the bottom, unplug the wires... (two connect to the window grid, mark which one is which)... and the module is free.
The module may require re-soldering of the pins joining the main power connectors to the internal circuit board. If you feel you can do this (or have a friend do it for you), go for it... else get another module from the dealer to replace it."

This is the most credible of the several posts that I've seen talking about this module. I know its there... I saw it yesterday when I was working on the car.

Depends, could be defroster could be antenna for radio, could be both. IF you don't see an antenna on your hood on passenger side then its most likely the antenna.