Voltage Drop Test

Voltage drop is the amount of voltage lost as it passes through a component or resistance in a circuit. In order to perform a voltage drop test, voltage must be present in a circuit. It’s the difference between voltage at the source or battery and the voltage at the component. The meters leads are connected in parallel with the circuit being tested.

It’s common to perform a voltage drop test on the starter circuit. This is because a voltage drop test is the best way to find resistance in a high current circuit. Test the positive battery cable, negative battery cables, and the starter solenoid. Check these readings against manufacturer’s specifications.

Perform voltage drop tests on the battery cable terminals and connections to the battery posts, engine block, and starter terminal. Terminals and connections should be clean and tight-fitting with little or no discernible voltage drop. Typically the standard for this cable is no more than 0.5 Volt depending on the vehicle. Some inexpensive replacement battery cables may have a thicker insulation and less conductor than the original cables.