Battery (Parasitic) Load Test

When a vehicle exhibits a low or dead battery after an overnight set, or goes down over a two or three day period, the electrical system should be checked for an excessive electrical drain using the "Parasitic Draw Test." This test should be performed after the battery has been recharged and load tested, and the charging system has been tested and is operating to specifications.

Parasitic Draw Test:

TOOLS NEEDED:
- J 38758 Parasitic Draw Test Switch

NOTE: The parasitic draw test switch should never be turned to the "OFF" position with the engine running; damage could occur to the attached ammeter or the vehicle electrical system.

1. Remove battery cable from battery negative terminal.
2. Install the parasitic draw test switch male end to negative battery terminal.

TIGHTEN
- J 38758 to 15 Nm (11 lb. ft.).

3. Turn test switch knob to the "OFF" position.
4. Install negative battery cable to female end of the test switch tool.

TIGHTEN
- Negative battery cable to 15 Nm (11 lb. ft.).
5. Turn the test switch knob to the "ON" position.

7. Turn ignition switch to the "Lock" position and remove ignition key.
8. Connect J 39200 terminals on test switch tool.
9. Turn test switch tool knob to the "OFF" position to allow current to flow through the ammeter.




10. Check Current reading. When current reading is at or below two amps, turn the test tool knob to the "ON" position (to maintain continuity in the electrical system) and switch down to the two amp scale for a more accurate reading when drain test tool knob is turned "OFF". When current reading is above two amps, refer to Parasitic Draw chart for the specific microprocessor "time outs".

REMOVE OR DISCONNECT

- Always turn the test tool knob to the "ON" position before removing each fuse to maintain continuity in the electrical system and to avoid damaging the ammeter due to accidental overloading (i.e.opening door to change fuse, etc.).




11. When current draw is less then 30 milliamps, check charging system for proper operation. When current draw is above 30 milliamps, remove system fuse one at a time until the current returns to a value less then or equal to 30 milliamps. Perform steps 8 through 10 each time a fuse is removed. Refer to Parasitic Draw chart for typical and maximum parasitic loads for various vehicle components.

REMOVE OR DISCONNECT

- Repeat parasitic current drain procedure after any repair has been completed.

12. When cause of excessive current draw has been located and repaired, remove current drain test tool and connect negative battery cable to negative battery terminal.

TIGHTEN
- Negative battery cable bolt to 15 Nm (11 lb.ft.).