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Old 10-16-2017, 01:32 AM   #1
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How to Find a Parasitic Battery Drain

Video tutorial on how to find a battery drain on your vehicle. So a battery drain, also known as a parasitic drain is a load on your electrical system which should be there that will eventually dissipate the charge in your battery. This occurs when your vehicle is off and can take anywhere from a couple hours to over a week depending on the severity of the drain. For this I am using a 1998 Ford Ranger as an example. Depending on the vehicle you are working with, some vehicles such as this Ranger may have a peak load period. After a certain time, this could be anywhere from 10min to 45min where the computer will eventually go into a sleep mode and the voltage draw will eventually. This is something which you’ll need to consult with your manufacturer’s specification in order to determine if there is a drop off period and how long it may take if there is one.

Tools/Supplies Needed:
-jumper wires
-ratchet and socket set

-remove the negative battery terminal
-considering my alligator clips won’t open wide enough to clip on the battery terminal, while this may look a little awkward, I’m using locking pliers
-a continuity test can be done across the battery post, through the pliers and jumper wire to ensure there is no resistance which may affect the accuracy of your readings
-to setup your multimeter, there should be an extra port to move the positive probe over for the amperage test, this one is rated for 10A, then set the amperage on the 10A setting
-connect the jumper wires to the test probes, one goes from the vehicle’s negative battery terminal clamp and the other goes to the battery terminal
-as you can see we currently have a 1.68 to 1.7 amp draw
-ensure all accessories are off in the vehicle which can include anything from the ignition being on, radio, fan, and lights
-we can source out the fault by pulling fuses, usually there will be more than one fuse box in a vehicle
-this can be around the dashboard area, in the engine compartment, trunk, or under a seat. Starting with under the hood
-so pulling this one fuse, you can see we have a drop but not nearly enough to put a large drain on a battery
-moving onto the interior of the vehicle, as mentioned before the door needs to be open in order to access the fuse panel
-again going through the fuses, pulling each one and watching the member to drop in value
-in order to determine what this circuit controls, take the number from the fuse location first
-pull out your vehicle’s owner’s manual, flipping over to the fuse section, determine what the circuit controls
-this was number 25 which is for the generic electronic module and gauge cluster, therefore we could have an issue with the gauge cluster or generic module
-for the fuses under the hood, referring the location of fuse 4, this was controlling the circuit fog lights and daytime running lights
-in order to determine what is the issue, you may have a stuck relay, faulty module, faulty switch, short in the wiring, etc
-you will need to consult with a wiring diagram specific for your vehicle to determine what exactly is on that circuit and start unplugging specific controllers to see what removes the parasitic draw. You can even do an online search to determine if there is common faults with your specific vehicle, Rangers are actually known for having the generic electronic module fail which is located behind the radio
-depending on the failing controller, these can sometimes be tested using a multimeter instead of wasting money on replacement items which isn’t even faulty
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