How To Do A Current Draw Test

Measuring Parasitic Describe

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

In order to cheque for parasitic draw, a Digital Multi-Meter (DMM) that can handle a minimum of ane milliamp and upwardly to ten amps is needed to perform a parasitic depict test.

Vehicle Preparation

one. Showtime 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 describe test. In add-on to diagnosing and charging a weak bombardment (or if you installed a new one to replace a dead ane) make sure to verify that the charging system is operating properly.

two. Turn the ignition OFF, and so make sure all electric accessories are OFF, too. This includes unplugging anything plugged in a power socket(s).

3. Disconnect the electric connector for the Anti-Theft Organisation Hood Switch (if equipped).

iv. Close the Hood.

5. Operate the vehicle to simulate customer operation. Run the engine, bulldoze the vehicle, stop the engine, release the hood latch, leave and lock the vehicle.

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

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

b. Move the DVOM red lead to the Amps position in the meter.

Vehicle Preparation for Measurement

1. Open up the Hood.

2. Wait at least 60 minutes to allow all systems to enter slumber mode. To get a right reading, the vehicle should be left with the doors closed and the ignition OFF for an hour before beginning the examination.

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

The virtually difficult role of making a parasitic depict measurement is establishing a "shunt" connection through your DVOM prior to disconnecting the concluding cablevision from the negative battery mail service.

a. Loosen, just Practice Not remove the negative battery concluding.

b. Connect the red atomic number 82 to the negative battery cable end.

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

4. Carefully remove the negative bombardment cable without breaking the shunt connection while removing the final cablevision from the bombardment post. Brand sure the DVOM leads remain fastened to the battery post and cable end. It'southward imperative that you keep this connectedness to avoid sending 1 of the modules back into an initialization process which boosts current flow. This may non blow the meters fuse, but it will definitely requite you an incorrect reading. You volition accept to wait until that process completes and they are set up to go to sleep before you lot can try again. The Ammeter should and so exist able to give y'all an accurate Parasitic Depict (Dark Current) measurement.

Determining the Source of Parasitic Draw

If the ammeter reading exceeds 23 mA, something may be using also much power. If excessive parasitic describe is nowadays information technology will need to be corrected then the bombardment does not drain. To make up one's mind the source of Parasitic Draw (Dark Current), start by checking for aftermarket accessories. If any aftermarket accessories are nowadays, remove the power to these accessories, and then retest.

Finally, follow normal diagnostic procedures to identify source of describe. If yous have a high reading, you'll demand to check each component. For case, remove fusible links, fuses, relays, etc., one at a time until the draw is isolated to the offending electric component/system. Open up the door, and record the door switch open circuit so that the system returns to sleep mode. Then, remove each fuse one at a time to isolate the circuit causing the draw.

The under hood fuses can be removed without too much difficulty, and without waking upwards the BCM. If you tin can't identify an excessive draw past removing the fuses, and the components check out fine, y'all may accept a wiring trouble.

Tabular array of Contents

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

Posted by: cashhincir.blogspot.com

Share this post