Voltage Drop Test

It is done with a multimeter connected across the part being tested, with the circuit switched on. Typical tests cover battery cables, ground straps and starter circuits during cranking. It finds faults that a simple continuity test misses. Many technicians use it as the first test for slow cranking or intermittent electrical faults, because it shows exactly where voltage is lost in a loaded circuit.

Any resistance causes a voltage difference when current flows; the meter shows how much is lost.

A drop of more than a few tenths of a volt on a starter cable usually points to corrosion or a loose connection. Measure during load, not with the circuit off.