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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1912 (Battery, Charging System And Starting System) >> Diagnostic Information and Procedures >> Battery Electrical Drain/Parasitic Load Test >> Parasitic Current Drain Testing With an Ammeter

Parasitic Current Drain Testing With an Ammeter

WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Turn the ignition and all accessories OFF and remove the key from the ignition switch.
  2. Disconnect the cable from the negative battery terminal.
  3. Follow the manufacturers instructions for the multimeter or ampmeter being used. This could involve plugging leads into different locations on a multimeter and changing the scale to read amperage. On some testers you should start on the 10 amp scale setting, and after verifying that current drain is less than 2 mA, set the scale to 200 mA or 20 mA.
  4. Touch the negative battery cable to the negative battery terminal, and hold them together for 20 seconds. This will allow the modules on the vehicle to wake up.
  5. While still holding the cable against the battery, connect the ammeter between the negative cable and the negative battery terminal so that it will be in series. Then remove the cable from the battery. Read the parasitic current drain from the battery.
  6. For vehicles with electronic power steering, wait 45 minutes for the modules to go to sleep. Otherwise, wait 20 minutes for the modules to go to sleep. The current draw may be greater than 100 milliamps for the first 2-5 minutes, then it should drop to 10-30 milliamps.
  7. To find the source of excessive load, start removing fuses and modules in a systematic way. When voltage drops across the tester, the circuit or circuits protected by that fuse is the source of current drain. Also remove the fusible link from the generator to check for a voltage drop. If the voltage drop is greater than 2 volts, replace the generator. Repair the circuit and perform the parasitic load test again to verify the repair.
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