Parasitic Load Test
TOOLS REQUIRED^ J 38758 Parasitic Draw Test Switch Tool
^ J 39200 Digital Multimeter
NOTE:
^ Do not turn the parasitic draw test switch to the OFF position with the engine running. Damage will occur to the vehicle's electrical system.
^ The test switch must be in the ON position when removing the fuses in order to maintain continuity in the electrical system. This avoids damaging the digital multimeter due to accidental overloading, such as a door being opened to change a fuse.
If a vehicle exhibits a low or dead battery after sitting overnight or discharges over a period of two or three days, the electrical system should be checked for an excessive electrical drain. This condition is referred to as parasitic load drain. To properly diagnose this condition, perform the Parasitic Load Test.
1. Turn the ignition to LOCK.
2. Charge the battery to a full state of charge. Refer to Battery Charging.
CAUTION: Refer to Battery Disconnect Caution in Service Precautions.
3. Disconnect the negative (-) battery cable.
IMPORTANT: The switch knob on the J 38758 is marked ON and OFF. When the switch knob is in the ON position, the circuit is closed and electrical current will pass through the switch. When the switch knob is in the OFF position, the circuit is open and electrical current will not pass through the switch.
4. Turn the J 38758 knob to the OFF position.
5. Connect the J 38758 between the battery and the negative battery cable.
6. Turn the J 38758 knob to the ON position.
7. Road test the vehicle and activate all of the accessories, including the radio and the air conditioning.
8. Park the vehicle. Turn the ignition switch to the OFF position and remove the ignition key.
9. Set the J 39200 to the 10 amp scale.
10. Connect the J 39200 to the test switch tool terminals.
11. Turn the J 38758 knob to the OFF position. The current now flows through the digital multimeter.
12. Measure the parasitic load draw (in amperes) with all doors closed and the ignition key removed from the ignition switch.
NOTE: The test switch must be in the ON position when removing the fuses in order to maintain continuity in the electrical system. This avoids damaging the digital multimeter due to accidental overloading, such as a door being opened to change a fuse.
13. If a parasitic load drain over 0.5 amperes is present, isolate the electrical system, circuit or component at fault by removing the fuses one at a time. Refer to Fuse Block Details Schematics.
14. If a parasitic load drain over 0.5 amperes is still present, check the generator, the starter motor, the starter solenoid and the related wiring for short circuits. Refer to Starting and Charging Schematics.
15. If a parasitic load drain less than 0.5 amperes is present, set the J 39200 selector switch to Milliamp/Microamp Input Terminal scale.
16. Measure the parasitic load draw (in milliamperes) with all doors closed and the ignition key removed from the ignition switch.
17. Normal parasitic load drain is 10 to 25 milliamperes. If the parasitic load drain is more than 25 milliamperes, isolate the electrical system, circuit or the component at fault by removing the fuses one at a time. Refer to Starting and Charging Schematics.
18. If a parasitic load drain over 25 milliamperes is still present, check the starter motor, the starter solenoid and the related wiring for short circuits. Refer to Starting and Charging Schematics.
IMPORTANT: Repeat the parasitic load test procedure after any electrical repair has been completed.
19. When the cause of the excessive parasitic load drain has been located and repaired, disconnect and remove the J 39200 and the J 38758.
NOTE: Refer to Fastener Notice in Service Precautions.
20. Connect the negative (-) battery cable.
Tighten
Tighten the negative (-) battery cable-to-negative (-) battery terminal retainer to 15 N.m (11 lb in).