Voltage drop testing a heated backglass element will help in understanding this often confusing and avoided test. With the system on, check voltage drop across the entire grid by measuring between the positive and negative terminals. You should see about 10 volts dropped, this is the voltage dropped across the total grid. Now connect the ground lead to a good chassis ground and starting in the center of the grid, measure volts on each trace of the grid and you should see about 6 volts. If you see 0 volts, the trace is broken towards the positive side of the grid. (B) If you see more than 6 volts, the trace is broken towards the negative side of the grid. (A) All traces should show diminishing or dropping voltage amounts as you move toward the negative side of the grid. This shows how all along the path of the trace, voltage drop increases as you get closer to ground, and decreases as you move closer to positive. The farther away from the positive side increases resistance on the circuit, and is indicated by more voltage drop.