Troubleshooting Unknown Battery Drain

If your battery drains after sitting a few days in your car, truck, motorcycle, tractor, camper or other fused circuit, this can be easily troubleshooted with below steps using a multimeter.

Before testing, make sure you have a fully charged battery installed and there is no corrosion on your battery terminals causing an insulation barrier between the battery and the terminals. Corroded battery posts not only prevent the vehicle from starting, but also prevent the battery taking charge from the alternator, external charger, or a jump from jumper cables.

  1. Key/power in off position
  2. Locate fuse box(es)
  3. Pull out a fuse
  4. In current setting, place multimeter leads across both terminals where the fuse was located to measure current, most should read somewhere between 0-100mA (zero or near zero is better) -you may want to start in a higher current rating initially when testing each fuse holder to prevent internal multimeter fuse from popping, and then switch to a lower mA setting
  5. Repeat this measurement across each active fuse holder
  6. If current is more than this in a given circuit, this will point you to what circuit is draining the power when key/power is off
  7. Look at label inside fuse box cover, owners manual, or internet schematic to identify circuit function of the failing circuit and what sensor, module, or assembly can be replaced to fix the issue -if the part is too expensive to replace or you want to get by, you can always unplug the fuse when not in use to prevent battery drain

See also:
Preventing and Treating Contact Oxidation
Chemicals, Cleaners
Electrical, Specialty Fuses
Test and Measurement Fuse Accessories
Rechargeable Batteries
Battery Chargers

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