With Ammeter, In-Line Test Procedure

WARNING: DO NOT ATTEMPT THIS TEST ON A LEAD-ACID BATTERY THAT HAS RECENTLY BEEN RECHARGED.

CAUTION: Do not crank on the engine or operate accessories that draw more that 10 A.

NOTE:
- Many modules draw 10 mA or more continuously.
- Typically, a drain of approximately one amp can be attributed to an engine compartment lamp, glove compartment lamp, or luggage compartment lamp staying on continually. Other component failures or wiring shorts may be located by selectively pulling fuses to pinpoint the location of the current drain. When the current drain is found, the meter reading will fall to an acceptable level. If the drain is still not located after checking all the fuses, it may be due to the generator.
- To accurately test the drain on a battery, an in-line digital ammeter must be used. Using a test lamp or volt meter is not an accurate method due to the number of electronic modules.

1. Make sure battery junction and central junction boxes are accessible without turning on interior and underhood lights.
2. Drive vehicle at least 5 minutes and over 30 mph to turn on and exercise vehicle systems.
3. Allow vehicle to sit with the key off for at least 1 hour to allow modules to time out/power down.
4. Connect a jumper wire between negative battery cable and negative battery post to prevent modules from resetting and to catch capacitive drains.
5. Disconnect negative battery cable from post without breaking the connection of the jumper wire.
6. Connect the Starter, Alternator, Battery, Regulator, Electrical Tester between negative battery cable and post. The meter must be capable of reading milliamps and should have a 10 amp capability.


NOTE: It is very important that continuity is not broken between the battery and the negative cable when connecting meter. If this happens the entire procedure must be repeated.

7. Remove jumper wire.


NOTE: If the meter settings need to be switched or the test leads need to be moved to another jack, the jumper wire must be re-installed to avoid breaking continuity.


8. Note AMP draw. Draw will vary from vehicle to vehicle depending on the equipment package. Compare to comparable vehicle for reference. No stock vehicle should have more than 50 mA draw.
9. If the draw is found to be excessive, then remove fuses from the central junction box one at a time and note current drop. Do not re-install the fuses until you are finished testing.
10. If the draw is found to be excessive, then remove fuses from the Battery Junction Box (BJB) one at a time and note current drop. Do not re-install the fuses until you are finished testing.
11. Check for any circuits that run from the battery without passing through the BJB. Disconnect these circuits if the draw is still excessive.