How To Find A Parasitic Draw On A Car

Measuring Parasitic Draw

All vehicles describe some power from their batteries when the car is shut off. Vehicles with onboard computers have Random Access Retention (RAM). And accessories such every bit clocks, audio systems (station presets), seats (Automatic Drive Positioner, or ADP), remote door openers, and security systems likewise need power to maintain retention when the ignition is OFF. Each device with memory has a dissimilar corporeality load. The power used as a result of this continuous energy or cumulative load is called parasitic draw. It is usually a very pocket-sized draw and so the bombardment doesn't become drained. Parasitic loads can run xx to 120 milliamps. If there is an electrical brusk in the vehicle or a malfunctioning accessory it could draw more its normal load causing a big drain on the battery.

In order to cheque for parasitic draw, a Digital Multi-Meter (DMM) that tin handle a minimum of ane milliamp and up to 10 amps is needed to perform a parasitic draw examination.

Vehicle Preparation

1. Outset prepare the vehicle for the parasitic describe test by making sure the battery is charged. Weak batteries don't give accurate results when performing a draw test. In addition to diagnosing and charging a weak bombardment (or if you installed a new ane to replace a dead one) brand sure to verify that the charging system is operating properly.

two. Plough the ignition OFF, and then make certain all electrical accessories are OFF, too. This includes unplugging anything plugged in a power socket(s).

three. Disconnect the electrical connector for the Anti-Theft System Hood Switch (if equipped).

four. Shut the Hood.

v. Operate the vehicle to simulate client operation. Run the engine, drive the vehicle, terminate the engine, release the hood latch, exit and lock the vehicle.

6. Digital Volt Ohm Meter (DVOM) Preparation (refer to the operating instructions provided with meter).

a. Set up DVOM to measure DC Amps on the highest scale (usually 10A).

b. Movement the DVOM ruddy lead to the Amps position in the meter.

Vehicle Training for Measurement

1. Open the Hood.

2. Wait at to the lowest degree lx minutes to permit all systems to enter sleep manner. To become a correct reading, the vehicle should exist left with the doors closed and the ignition OFF for an hr before showtime the test.

3. Select Ammeter, and and so connect the leads.

The most difficult part of making a parasitic draw measurement is establishing a "shunt" connection through your DVOM prior to disconnecting the concluding cable from the negative battery post.

a. Loosen, but Do Not remove the negative battery final.

b. Connect the ruby lead to the negative battery cable end.

c. Connect the black pb to the negative battery post.

4. Advisedly remove the negative battery cable without breaking the shunt connection while removing the terminal cable from the battery postal service. Brand sure the DVOM leads remain attached to the battery post and cable stop. It'due south imperative that you keep this connexion to avoid sending one of the modules back into an initialization process which boosts current period. This may not accident the meters fuse, simply it will definitely give yous an wrong reading. You will have to wait until that procedure completes and they are ready to get to slumber before you can try once more. The Ammeter should then be able to requite you an authentic Parasitic Depict (Dark Electric current) measurement.

Determining the Source of Parasitic Draw

If the ammeter reading exceeds 23 mA, something may exist using too much power. If excessive parasitic draw is present information technology volition need to exist corrected and so the bombardment does not bleed. To determine the source of Parasitic Depict (Night Electric current), outset by checking for aftermarket accessories. If any aftermarket accessories are present, remove the ability to these accessories, and so retest.

Finally, follow normal diagnostic procedures to identify source of draw. If you lot have a high reading, you lot'll need to check each component. For example, remove fusible links, fuses, relays, etc., ane at a time until the describe is isolated to the offending electrical component/organisation. Open the door, and record the door switch open up circuit so that the arrangement returns to sleep fashion. And then, remove each fuse i at a time to isolate the circuit causing the describe.

The under hood fuses can be removed without too much difficulty, and without waking upwards the BCM. If you lot can't identify an excessive depict by removing the fuses, and the components check out fine, you may take a wiring trouble.

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Source: http://www.nissantechnicianinfo.mobi/htmlversions/Winter_2012/Parastic_Draw.html

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