Once the surface layer of the grid has either been scratched or in the noted cases above “peeled”, the grid will absolutely NOT work on those damaged lines.
To examine defroster girds:
You need 2 people to do it right. Person 1 is on inside of the vehicle. Person 2 stands on the outside of the vehicle. Person 2 on outside needs to use a good bright flashlight and is to shine the light over each grid line. Pick one line and move slowly over it left to right. If you see any breaks in the line at all (let alone the obvious peeling), those grid lines are damaged. Even if there is a very thin hairline fracture in the line, it won’t work because the line is breached, similar to cutting a wire in half.
There is a Ford defroster repair kit - but it is a tedious process. It’s a small jar with applicator brush and the user has to apply the solution to each broken area of the grid line. Usually best application is to tape off either side of the line - but not everyone has a steady hand taped or not. Once the repair kit is used - there’s no guarantee the “fix” will work. If you were to tint the window, you would definitely see discoloration of those repaired lines in the tint.
The glass should be replaced, especially under the Ford New Car 3/36 Warranty.
Attached GSB G0000179, page 6 outlines that the above issues ARE Warranty items:
