Car Battery Keeps Dying?

How to Perform a Parasitic Draw Test

Maybe you installed a new battery or alternator and now your vehicle won’t start. Maybe your car battery dies overnight, after sitting for a few days, or keeps dying but the alternator and battery is good. If your battery keeps dying when you try to start your vehicle and you know it’s in good condition, chances are a parasitic draw is draining the battery from a light or a module that may be stuck on. This post explains how to perform a parasitic draw test with a tester tool and a multimeter to find out what’s draining the battery and how to fix it.

Perform a parasitic draw test and fix the cause yourself with quality auto parts and tools at

How to Perform a Parasitic Draw Test in 9 Steps

Steps for Performing a Parasitic Draw Test

  1. Charge the Battery

    Charge the battery with a battery charger or make sure the battery is charged before beginning

  2. Find a Battery Shut Off Tool or Parasitic Draw Tester Tool

    You will need a battery shut off tool or a parasitic draw tester. This tool basically fits between the battery and the negative battery cable. It requires you to road test the vehicle with all the electronics on, such as the radio, heating and air conditioning, cruise control, and connect a multimeter to either end of the tool to get a reading without disrupting the modules.

  3. Remove the Fuse Panel Covers

    Remove the fuse panel covers to access them easily.

  4. Close the Door Latches or Dome Light Switches

    If the vehicle has dome lights connected to the latch, close the latches. If you have a dome light switch, push these down as well.

  5. Connect the Multimeter to the Shut off Tool

    Connect the multimeter to the tool. Each multimeter is different, but connect the positive lead to the 10 amp max fuse setting. Set the dial to milliamps. Hook a lead to each side of the tool (doesn’t matter which side).

  6. Let the Modules Power Down

    You want the modules to power down before opening the switch on the tool or else it will put a draw on the battery, which is normal. On older vehicles it takes about 10 minutes for the modules to power down. On newer vehicles it could take up to an hour for the vehicles to power down.

  7. Open the Switch and Take a Reading

    Open the switch on the parasitic draw tester tool. Read the reading of milliamps on the screen. Wait up to 10 minutes to an hour to see if the reading falls below 30 milliamps.

    If lights are on the reading can be much higher.

    Don’t open any doors or unlatch any latched door latches while the multimeter is taking a reading or it could blow a fuse in the meter.

  8. Remove One Fuse at a Time

    To find out where the draw is originating, remove one fuse at a time and check the meter. If the reading falls, that fuse’s circuit is probably causing the parasitic draw.

    When reinserting the fuse, depending on what circuit it is in, it may turn on a module on and you may have to wait a minute or two if the reading spikes. If it significantly spikes or drops, you’ll probably have to wait another 10 minutes for the module power down before pulling the next fuse.

    We recommend pulling one fuse per circuit to save hassle when reinstalling the fuses.

  9. Check Any Fuse’s Circuits with Low Readings

    If the reading drops below the fuse’s amps, check that circuit by reconnecting the fuse to the circuit and disconnecting the suspected part from the circuit. If the parasitic drawing stops, that part is the cause.

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Car Battery Keeps Dying? How to Perform a Parasitic Draw Test - 1A Auto
Article Name
Car Battery Keeps Dying? How to Perform a Parasitic Draw Test - 1A Auto
A car battery with parasitic draw will keep dying overnight, every few days, or whenever you start when you know it's in good condition. This post explains how to perform a parasitic draw test and fix the cause of a parasitic draw.
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1A Auto
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