HOW TO PERFORM A PARASITIC DRAIN TEST
A parasitic drain is frustrating to deal with since it can be intermittent and often leaves you with a dead battery when you least expect it. In some cases, it can be severe enough to deplete your fully charged battery overnight. Although you can test any circuit for a parasitic draw, this is how it works for a draw on an alternator, and all you need is a digital multimeter.
Fully charge the battery. For accurate results and enough time to finish testing, a full battery is recommended.
Turn off powered devices. Remove the key from the ignition, accessories you have plugged in, turn off your dome light, and wait at least 30 minutes for computer modules to go to “sleep”.
Test circuits for power where there shouldn’t be any. Place the multimeter into the DC milliamps setting and connect its black cable to the battery’s negative post. Probe the negative battery cable with the red lead on the multimeter set to the highest limit, then slowly turning it down until it detects amperage. If you have much more than 50 milliamps of draw, there’s a parasitic load in your car.
Next, remove the alternator fuse and recheck for draw. If the parasitic draw is gone, the alternator is to blame.
Perform an alternator diode test. To confirm your suspicion, set your multimeter to AC Volts (ACV) and reconnect the battery cable. With the engine running, touch the red lead to the positive battery post and the black lead to the negative post. If there’s more than 0.5 ACV, the alternator likely has one or more bad diodes.
credit :autozone
@bobnizam
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2 окт 2024
