ASE Electrical and Electronic Systems (A6) Practice Test

When conducting a rear defogger grid test, a reading of the same voltage on both ends signifies that there is an open circuit in the grid line. In a properly functioning grid, voltage should decrease along the grid due to resistance; thus, if the voltmeter provides identical readings at both ends, it suggests there is no current flow through the grid, indicating a break in the conductive path.

This situation typically arises from a broken wire or connection within the grid itself, which prevents electricity from passing through. In contrast, short circuits would create a condition where the voltage drops to zero due to a direct connection bypassing the resistance of the grid. Loose connections in the ground could lead to intermittent voltage readings, and a faulty voltmeter would compromise measurement accuracy altogether. Therefore, seeing the same voltage at both ends directly points to an open circuit in the grid line.