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 50 minutes after the doors have been opened before performing this test.
• Many computers draw 10 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 milliamperes 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. Turn the switch to mA/A dc.
3. Disconnect the battery terminal and touch probes.
4. Isolate the circuit causing the current drain by pulling out one fuse after another while reading the display.
5. Current reading will drop when the fuse on the bad 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 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.

Electronic Drains which Shut Off when the Battery Cable is Disconnected

1. Repeat Steps 1 through 6 of the drain testing.
2. Without starting the engine, turn the ignition ON for a moment and then OFF. If applicable, wait one minute for the illuminated entry lamps to turn off.
3. Read the current from the multimeter.