Starter Current Draw Test

Automotive Battery Test

A starter current draw test is performed after the battery been inspected and charged if necessary. The starting system should also be visually inspected for any physical defects or loose connections. Bring the engine to normal operating temperature before performing this test. This is because a cold engine requires more current than a warm engines does.

Digital multimeter ammeter

Use an ammeter/voltage meter that has been recommended by the vehicle manufacturer. This test requires the specifications for the vehicle being tested.

  1. Connect the test leads to the positive and negative terminals and then connect the clamp-on amp pickup around one of the battery cables.
  2. Set the voltage meter to Int 18V and adjust ammeter to read zero.
  3. Disable the fuel or ignition so the engine will not start during test.
  4. Crank the engine as you observe the testers ammeter and voltmeter.
  5. Never crank the engine for more than 15 seconds and allow the starter to cool for 2 minutes between cranks.

Observe the voltage and the amperage at the same time. The voltage should remain at or above specifications while cranking the engine. High current draw and low cranking speed indicate a faulty starter or possible engine problems. Low cranking speed and low current draw indicate excessive resistance in the starter circuit. Always check specifications; the bigger the engine the higher the current draw.

Slow cranking and high current draw typically indicate worn bearings or bushings inside the starter. Worn bushings result in an off-center armature. This can result in poling and can throw off the alignment of the starter’s magnetic fields.