how to test for parasitic draw

Measuring Parasitic Draw

All vehicles draw some ability from their batteries when the car is shut off. Vehicles with onboard computers have Random Admission Memory (RAM). And accessories such as clocks, audio systems (station presets), seats (Automatic Drive Positioner, or ADP), remote door openers, and security systems too need power to maintain retentiveness when the ignition is OFF. Each device with memory has a different amount load. The power used every bit a upshot of this continuous energy or cumulative load is called parasitic describe. It is usually a very small draw so the bombardment doesn't become drained. Parasitic loads can run 20 to 120 milliamps. If there is an electric short in the vehicle or a malfunctioning accompaniment it could draw more than its normal load causing a large drain on the bombardment.

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

Vehicle Preparation

1. Beginning prepare the vehicle for the parasitic draw exam by making sure the battery is charged. Weak batteries don't give accurate results when performing a depict test. In improver to diagnosing and charging a weak battery (or if you installed a new 1 to replace a dead ane) make sure to verify that the charging arrangement is operating properly.

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

3. Disconnect the electrical connector for the Anti-Theft Organization Hood Switch (if equipped).

four. Close the Hood.

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

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

a. Set DVOM to measure DC Amps on the highest calibration (ordinarily 10A).

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

Vehicle Preparation for Measurement

one. Open the Hood.

2. Expect at to the lowest degree 60 minutes to allow all systems to enter sleep manner. To get a correct reading, the vehicle should be left with the doors airtight and the ignition OFF for an hour before first the exam.

3. Select Ammeter, and then connect the leads.

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

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

b. Connect the red lead to the negative bombardment cable stop.

c. Connect the black lead to the negative battery mail.

4. Carefully remove the negative battery cable without breaking the shunt connection while removing the terminal cable from the battery post. Make sure the DVOM leads remain attached to the battery post and cablevision end. Information technology'south imperative that you keep this connection to avoid sending 1 of the modules dorsum into an initialization process which boosts current flow. This may non blow the meters fuse, merely it will definitely give you an incorrect reading. You will have to expect until that procedure completes and they are ready to go to slumber before you can effort again. The Ammeter should then be able to give you lot an accurate Parasitic Draw (Night Current) measurement.

Determining the Source of Parasitic Draw

If the ammeter reading exceeds 23 mA, something may exist using also much power. If excessive parasitic describe is present it volition need to exist corrected so the battery does not drain. To make up one's mind the source of Parasitic Draw (Dark Current), commencement by checking for aftermarket accessories. If any aftermarket accessories are present, remove the power to these accessories, and then retest.

Finally, follow normal diagnostic procedures to identify source of draw. If you lot take a high reading, you'll need to check each component. For instance, remove fusible links, fuses, relays, etc., i at a time until the draw is isolated to the offending electric component/organization. Open the door, and record the door switch open circuit so that the system returns to sleep mode. And then, remove each fuse one at a time to isolate the excursion causing the draw.

The nether hood fuses tin can be removed without as well much difficulty, and without waking up the BCM. If you can't identify an excessive draw by removing the fuses, and the components cheque out fine, you may have a wiring problem.

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

Posted by: whisleroulty1966.blogspot.com

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