Which of the following is not a mechanical failure for a power window system?

• A. Broken window regulator
• B. Worn sash track
• C. Broken window motor gear
• D. Poor grounds

Answer: (D)

The main idea here is telling apart mechanical problems from electrical ones in a power window system. Mechanical failures involve the moving parts that actually drive the window: the regulator, the path it travels along (sash track), and the gear train inside the motor. If any of these parts break or wear, the window either won’t move or will move inconsistently due to a physical fault.

A broken window regulator is a direct mechanical issue—it's the mechanism that up-and-downs the glass. A worn sash track creates friction and resistance in the path the glass slides, which is also a mechanical problem. A broken motor gear disrupts the drive train inside the motor, another mechanical fault.

Poor electrical grounds, on the other hand, are an electrical issue. A bad ground can prevent adequate current from reaching the motor, causing the window to fail to operate or to operate erratically, but it isn’t a physical break or wear in the moving parts themselves. So the not-a-mechanical-failure choice is the grounding problem.