Battery Drain Test

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:
^ The technician must wait approximately five minutes after the doors have been opened before performing this test.
^ Many computers draw 10 milliamperes (mA) or more continuously.
^ Use an in-line ammeter between the battery positive or negative post and its respective cable.
^ Do not start the vehicle with a clip-on cable.

Check for current drains on the battery in excess of 50 mA with all the electrical accessories off and the vehicle at rest. Current drains can be tested with the following procedure:
1. Insert the test leads in the input terminals.
2. Set the multimeter to mA/A DC.
3. Disconnect either battery cable.
4. Connect the multimeter between the disconnected battery cable and its respective battery terminal.
5. If the current reading exceeds 50 mA, isolate the circuit causing the current drain by pulling out one fuse after another while reading the display. Current reading will drop when the fuse on the faulty circuit is pulled.
6. Reinstall the fuse and test components (including connectors) of that circuit to find the defective component(s).

Typically, a drain of approximately one amp can be attributed to an engine compartment lamp, glove compartment lamp or courtesy lamp staying on continuously. 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 drop to an acceptable level.