Drain Testing

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

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

NOTE:

- 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 short is still not located after checking all the fuses, the drain may be due to the generator.

- To accurately test the drain on a battery, an in-line digital amp meter 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 engine compartment and interior fuse panels 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 digital amp meter (DVOM) between negative battery cable and post. The meter must be capable or reading milliamps and should have a 10 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 a comparable vehicle for reference. No stock vehicle should have more than 50 MA draw.
9. If the draw is found to be excessive, pull fuses from the interior fuse panel one at a time and note current drop. Do not re-install the fuses until you are finished testing.
10. If the draw is still excessive, then remove fuses from the engine compartment fuse panel one at a time and note current drop. Do not re-install fuses until you are finished testing.
11. Check the wiring schematic in the EVTM for any circuits that run from the battery without passing through the engine compartment fuse box. Disconnect these circuits if the draw is still excessive.

TEST CONCLUSION
The current reading (current drain) should be less than 0.05 amps. If it exceeds 0.05 amps after a few minutes, and if this drain did not show in previous tests, the drain is most likely caused by a malfunctioning electronic component. As in previous tests, remove the fuses in the interior fuse junction panel one at a time to locate the problem circuit.