ABYC Diesel Practice Exam

How should a ground circuit resistance check (voltage drop) be conducted?

1. Check resistance at the battery terminals

2. Connect the voltmeter across the ground circuit while cranking

3. Use a visual inspection without electrical testing

4. Measure resistance only at rest

The correct answer is: Connect the voltmeter across the ground circuit while cranking

To effectively assess the ground circuit resistance, conducting a voltage drop test while cranking the engine is essential. This method provides a real-time evaluation of how well the ground circuit is functioning under load conditions, as the actual operational state of the components can lead to different readings than when they are at rest. When the engine is cranking, the system draws significant current, which can reveal issues that might not be evident under non-load situations. Measuring the voltage drop across the ground circuit allows you to identify any resistances that may be present, which could impede proper electrical function and result in poor engine starting or erratic electrical behavior. Performing this test ensures that you are getting an accurate representation of how the ground circuit performs when the engine is under normal operational loads. This approach is crucial for troubleshooting and diagnosing potential issues with electrical components that rely on proper grounding for efficiency.