Purchased a 1999 DeVille which had tinted windows that failed to pass Maryland Inspection. Went to a tint shop to have all tint professionally removed. It snowed yesterday. Tried the rear window defogger. Top 8 grid lines work. Bottom 4 lines do NOT. I looked inside and pulled rear trim panels slightly away from the sides revealing edges of the grid lines and a 1/4 inch or so heavy woven wire which runs the length of the grid lines vertically.
There does not seem to be any breaks in the wire or grid lines. How do I proceed from here? How do you test the continuity. Have a DVM and know how to use it but don't see any obvious breaks in the lines or the supply feed wires.[]

 

Grids are painted on window, you likely damaged grids. You can check them with test light. Test light should be bright on one side of glass and out on other. Running test light along grid - it should dim as you travel the lenght of each grid.

 

Used a DVOM and found 13+ volts on two of the lines. The bottom 2 lines are actually working but at reduced defogging. They are slightly longer and I guess that accounts for the difference
The 3rd and 4th lines from the bottom measure 13+ volts all across the gridline. Don' see a break either. At the end of the gridline is a larger metallic line attaching it to the braided supply line going vertically. Once again if I go from one braid on the passanger side (ground) to the other braid on the drivers side (battery + voltage) get 13+ volts. Can't find the break in these 2 lines but they don't work. I will try measuring resistance across the grid lines and compare to the line just above the two that don't work. Electrically it SHOULD. Any other suggestions?BIGHANK

 

Most of the time a DVOM is the ticket, however in this case you need to use test light.The defogger is basically a controlled short to ground using a large parallel circuit.The test light is a load on circuit that showing current flow to ground.