2005 Rear defroster not working

I think you have to bite the bullet and remove the trim! (There are many "how-to" videos on youtube!)
The first time you remove the inside trim of the rear hatch can be nerve-racking, and you just need to have faith and apply some brute-force! …but it gets easier each time! (…just take careful note of where the fasteners are located! …and a flat-bladed screwdriver or special removal-tool¹ can be most useful)
Do you have (…are you able to borrow) a Digital Multi-meter? Not having access to the correct tools will put you at a considerable disadvantage! - hope this helps - Wil
BTW: Welcome to PriusChat!

¹

 

Sounds like either a bad connector, or an open circuit in the wiring! Try wriggling the connectors, or even disconnecting and re-connecting or just cleaning, is sufficient some times! Good luck!

 

That would be possible if something scraped across all traces on the window, I suppose.

 

Perhaps something scraped the inside trashing the elements? Over-enthusiastic cleaning? …something like the corner of a box or something sharp scraping the inside of the glass as someone slammed the hatch a bit too hard? From what you describe, it certainly seems the whole thing is open-circuit. Are the heating elements inside the glass (i.e. physically part of the screen), or is it like a decal? Check the local junkyards to look for an intact rear-screen? (…then get your local auto-glass shop to replace it for you).

 

Many years ago, I had an issue with a couple of traces not working on a (non-Toyota) car that was under warranty. The dealer found the issue and repaired with some conductive paint? that looked silver on the inside of the car. It worked fine except the small repair areas did not tend to heat up.
This type of repair may be less expensive & troublesome than replacing the rear window.

 

…if your insurance covers glass, they might at least pay for the labour of replacing the screen (…now I'm not suggesting that you do the Center-PunchTrick¹ (…ooops! …well just look at that! I guess it must have been a stone, or some kid with a B-B gun! ) ) but you get the idea!!!

¹

 

I think I remember seeing something similar many moons ago (in the UK, on a mate's car), and it would make sense if the "fix" only provided continuity, and was not resistive enough to generate heat. A friend is an artist who engraves perspex/glass etc. with extremely finely-detailed line-art, if it were me, I'd ask him to try to engrave the broken traces, and fill with conductive paint as @Prodigyplace suggested!

 

We both forgot about the tint on the inside though

 

There is conductive paint made for nearly the exact job, repairing damaged traces on printed circuit boards. Friendly local electronics shoppes have it.

You can hook a battery across the window, connect the − lead of your meter to the − side of the battery, and just touch the + meter lead to the traces at different spots. (If you might have film or something over the traces, a sharp pointy + meter lead will help you contact the trace.)

A good trace will show you a voltage that goes proportionally with the position where you probe it, from 0 V at the − end to 12 V at the + end. A trace that is broken somewhere will show 0 V everywhere on the − side of the break, 12 V everywhere on the + side. Once you find it, apply the conductive paint.

You probably want to find all the breaks (this is all assuming that broken traces are your issue), then disconnect the battery to paint and let the paint dry before trying again with power.

Laying down some tape strips on either side of the existing trace will help you paint over a break in a way that matches the width of the trace.

If you have multiple breaks in a single trace, this method with the meter will find them in order, starting with the one closest to the + end.

Typically, a break is small enough that you don't really notice whether the conductive paint heats up less than the original conductor.

-Chap