Drain Test
DRAIN TESTWARNING: Do not attempt this test on a lead-acid battery that has recently been recharged. Failure to follow this instruction may result in personal injury.
CAUTION: Do not crank the engine or operate accessories that draw more than 10 amps, as this could blow the fuse in the multimeter.
NOTE: Many computers draw 10mA or more continuously.
NOTE: Use an in-line ammeter between the battery negative terminal and its respective cable.
Check for current drains on the battery in excess of 50 milliamps with all the electrical accessories and the engine switched off. Current drains can be tested with the following procedure.
1. Disconnect the battery ground cable.
2. Connect the black lead on the ammeter to the battery negative terminal.
3. Connect the red lead on the ammeter to the battery ground cable.
4. Isolate the circuit causing current drain by pulling out one fuse after another while reading the display.
5. Current reading will drop when the fuse on the relevant circuit is removed.
6. Install the fuse and test the components (including connectors) at that circuit to find a damaged component(s).
The current reading (current drain) should be less than 0.05 amp. If it exceeds 0.05 amp, it indicates a constant current drain which could cause a discharged battery. Possible sources of current drain are vehicle lamps (engine compartment, glove compartment and load space) that do not turn off correctly.
If the drain is not caused by a vehicle lamp, remove the fuses from the central junction box one at a time, until the cause of the drain is located. If the drain is still undetermined, remove the fuses from the battery junction box one at a time, until the cause of the drain is located.
Typically, a drain of approximately one amp can be attributed to an engine compartment lamp, glove compartment, or load space lamp staying on continuously.
If the short is still not located, after checking all the fuses and fuse links, the drain may be due to the generator.