While most mechanics know how to measure voltage, few master the art of voltage drop testing. This diagnostic method is superior to simple resistance checks because it tests the circuit under load.
Why Resistance Checks Lie
A single strand of copper wire can show 0.1 ohms on a multimeter, but it cannot carry the current needed for a fuel pump or starter motor. Voltage drop testing reveals these hidden flaws.
How to Perform the Test
- Set your multimeter to DC Volts.
- Connect one lead to the battery positive post.
- Connect the other lead to the load side (e.g., the starter positive post).
- Crank the engine. Any reading over 0.5V indicates high resistance in that cable.
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