Parasitic Current Drain Testing With An Ammeter

1. Turn the ignition and all accessories Off and remove key from ignition switch.
2. Disconnect cable from negative battery terminal.
3. Follow the manufacturer's instructions for the multimeter or ammeter 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 the current drain is less than two milliamps, set scale to 200 milliamps or 20 milliamps.
4. Connect ammeter between negative cable and negative battery terminal so that it is in series. Read parasitic current drain from battery.
5. To find the source of excessive load, start removing fuses in a systematic way. When voltage drops across the tester, the circuit or circuits protected by that fuse is the source of the current drain. Repair circuit and perform parasitic load test again to verify repair.




Typical Parasitic Loads
10-15 mA is typical. If vehicle does not have one or more of the following components or systems, then subtract the component's load from total vehicle parasitic load range (10-15 mA) to determine typical parasitic load range of vehicle being tested.

If the CD changer door is open and the light is illuminated, the parasitic current draw will be approximately 65 mA. The light will remain on for two minutes. Alter the light goes out, the CD changer parasitic current draw will stabilize at approximately 3 mA.

Typical Undesired Parasitic Loads
^ Park lamps On
^ Headlamps On
^ Dome lamp On
^ Map lights On
^ Cargo lamp On
^ Radio On
^ Cigar lighter On
^ Fog lamp switch On (will draw current even with ignition switch Off)