Operation CHARM: Car repair manuals for everyone.

Parasitic Load Test

1. Turn the ignition and all accessories Off and remove key from ignition switch.
2. Disconnect the cable from the negative battery terminal.





3. Install the parasitic load tester between the negative cable and the negative battery terminal so that the 1 ohm resistor is in series with the other resistances.

IMPORTANT: The alligator clamp on the parasitic load test device must be connected to the flat pad part on the negative battery cable. Do not connect the alligator clamp to the bolt on the negative battery cable; this will cause incorrect readings.




4. Set the multimeter to the MILLIVOLT scale.
5. Measure the current across the tester by putting the multimeter probes on two terminals on the end of the tester. The reading obtained is in volts. This reading is directly converted to milliamps. Should the parasitic current draw exceed 1 amp, the LED indicator on the test device will light. This may indicate that a vehicle accessory is On. For normal parasitic current drain, see individual component parasitic loads.
6. To find the source of the excessive load, start removing the fuses and modules in a systematic way. When the voltage drops across the tester, the circuit or circuits protected by that fuse is the source of the 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.