I manged to re-solder mine but it did not help as my little grid lines were corroded to the point there is many breaks in the circuit.

But, Ounce soldered with the Ohm and Volt meter I got conduction; but the grids were shot.
In my case I had the Rear Window Out to redo the Rear seal and rust repair.

__________________
84 300D, 82 Volvo 244Gl Diesel