Battery Tests

BATTERY - DRAIN TESTING

Check for current drains on the battery in excess of 24-26 milliamps (0.024-0.026 amp) with all the electrical accessories off and the vehicle at rest for at least 40 minutes. Current drains can be tested with the following procedure:

WARNING: Do not attempt this test on a lead-acid battery that has recently been recharged. Explosive gases can cause personal injury.

CAUTION: To prevent damage to the meter, do not crank the engine or operate accessories that draw more than 10A.

NOTE:
- Many electronic modules draw 5 mA or more continuously.
- Use an in-line digital ammeter between the battery negative post and its respective cable.

1. Make sure the central junction box is accessible without turning on interior or underhood lights.
2. Drive the vehicle at least five minutes and over 48 km/h (30 mph) to turn on and activate vehicle systems.
3. Allow the vehicle to sit with the key off for at least 40 minutes to allow modules to time out/power down.
4. Connect a jumper wire between the negative battery cable and the negative battery post to prevent modules from resetting and to catch capacitive drains.
5. Disconnect the negative battery cable from the negative battery post without breaking the connection of the jumper wire.
6. Connect the battery tester between the negative battery cable and post. The meter must be capable of reading milliamps and should have a 10 amp capacity.

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

7. Remove the 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 reinstalled to avoid breaking continuity.

8. Note the amperage draw. Draw will vary from vehicle to vehicle depending on the equipment package. Compare to a similar vehicle for reference. No factory equipped vehicle should have more than a 24-26 mA draw (0.024-0.026 amp).
9. If the draw is found to be excessive, pull fuses from the central junction box one at a time and note the current reading. Do not reinstall fuses until you have finished testing.
10. If the current draw is still excessive, remove the remaining fuses from the junction box one at a time and note the current drop. Do not reinstall fuses until you have finished testing. When the current level drops after pulling a fuse, the circuit containing the excessive draw has been located.
11. Check the Wiring Diagrams for any circuits that run from the battery without passing through the junction box. If the current draw is still excessive, disconnect these circuits until the draw is found. Also disconnect the generator electrical connections if the draw cannot be located. The generator may be internally shorted, causing current drain.