The plastic holding the electric defogging wires is discolored.
1) How can it be cleaned?
2) How can it be replaced if cannot be thoroughly cleaned?

The plastic holding the electric defogging wires is discolored.
1) How can it be cleaned?
2) How can it be replaced if cannot be thoroughly cleaned?
Normally on these, the defroster grid is built into the glass. Is this an aftermarket add-on defroster?

I'm guessing aftermarket is correct. The back of the car was crunched and they likely replaced the glass with something less expensive than the Toyota original. So, any suggestions?

Cleaning any plastic surface is sketchy at best.
What have you tried so far? What is on there that needs cleaned?
If it's outright color distortion, you'll likely need to replace the defroster or simply remove it and have just glass.

I think I used Simple Green to remove the dirt from the surface of the plastic film.
The film is discolored and I am hoping someone can recommend a product that will polish or remove the film discoloration.
Going without a defogger is not an option.

1) Guess I'll try some polish that's supposed to remove surface scratches from plastic windshields.
2) Any suggestions on a good aftermarket kit to replace window defogger strips? Guess I'll have to remove the glass
And do this if the polish doesn't work!

Thanks... Skip

I was wrong!! On closer inspection, everything appears to be Toyota and the grid is not built into the glass. I can feel it on the inside of the glass. The plastic film appears to be perhaps a very light tint. So it is not so much a discoloration but mostly distortion that makes it difficult to see through. My wife is adamant about wanting her view out the back improved but keeping the defroster. What might be the best way to remove the film without damage the grid which is mounted on the surface. And where is the grid connected to the wiring harness, on the sides, or the bottom, or top? Thanks!

If you have a factory defroster, heat the plastic film adhesive with a heat gun or hair dryer.
Keep it moving while gently pulling on the plastic. Heat may be applied from outside first unless it's found to be ineffective.
Again, just keep the heat moving. You want to release the adhesive, not melt any of the film.
Clean-up after as needed with a quality window cleaner and soft towel.