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View Full Version : how to diagnose a electrical short?



BlackDiamondBound
02-25-2013, 04:55 PM
Hi guys, I have a short that will drain the battery completely if the jeep if its not started in 7 days. I know this isnt good for the yellow top, but I should be able to get a new one under warranty and that time is getting close so its time to try and fix this thing. Dont really know too much about electrical stuff, perhaps you can give me some insight. This is what I have done

Used an ohm, not too sure what setting it was on but my friend said if its beeps there is a short. so grounded once side of the ohm meter then used the other side on each of the positive cables that run to the positive battery terminal. they were all disconnected of course. out of all of them I only had one that beeped, so I assume that is the one that is shorting and making contact somewhere. I followed it to where it spits. one goes to the alternator and the other goes to the fuse box under the hood. both beeped with the ohm meter.

and thats where im at. suggestions on what the next step is or if i did the above correct? thanks

SoCalDozer
02-25-2013, 05:10 PM
Disconnect the fuse box if you can. Best way to trouble shoot wiring is one section at a time and keep narrowing it down. I'm at work now or I could help walk you through it a little more.

This is the stuff I do for a living lol

BlackDiamondBound
02-27-2013, 11:41 PM
thank you for the response socaldozer! I started researching some different methods because i felt that the way I was doing it wasn't the best so i did something different ti find the battery drain. I took a 12v spare turn single bulb and wired it up with a positive and negative lead creating a test light. I then disconnected everything that was attached to the negative terminal. I read if you take the test bulb and connect one side to the negative terminal and the other side to the leads on the negative terminal the bulb should not light up. if it does there is a drain.

with that being said unfortunately all 4 of my leads going to the negative terminal on the battery lit up the bulb so looks like i have a little bigger drain then i thought. i'm going to leave the test bulb connected and start pulling fusses on at a time. if a fuse is pulled and the light turns off that is where to start looking next for the drain. hows this logic seem to you?

BlackDiamondBound
02-28-2013, 01:49 AM
update: I was able to pull two fuses and get the test light to turn off, so now i know at least what area to start looking. with the fuses still pulled, i disconnected the positive terminal then reconnected it and the test light illuminated for a couple seconds before going out. Is this a bad sign that the wiring is really jacked or is this okay?

SoCalDozer
02-28-2013, 02:29 PM
update: I was able to pull two fuses and get the test light to turn off, so now i know at least what area to start looking. with the fuses still pulled, i disconnected the positive terminal then reconnected it and the test light illuminated for a couple seconds before going out. Is this a bad sign that the wiring is really jacked or is this okay?

If its lighting up for a second then going out it sounds like there is still a leak, just not as bad as the others. Usually with something like this it is usually one main component that is doing it. How old is the alternator? And try disconnecting that as well

BlackDiamondBound
02-28-2013, 11:58 PM
same results with the alternator disconnected, but i read that this is normal for the light to illuminate then turn off because there is some current running threw the negative terminals till they are grounded which is why they spark when you put the on the battery terminal at first.

so i pulled 2 fuses 7 and 8 that were causing drains on the battery. my manual and all the electronic manuals online say fuse 7 is for interior lights and fuse 8 does other stuff like lift gate release. in my case fuse 8 does everything its suppose to and does fuse 7s as well. intieror lights only go on with fuse 8 in even tho fuse 7 is suppose to do that. :thinking: if i unplug the wiring harness in the back of the fuse box and reconnect with fuse 7 in the lights turn on for no reason. then i pull the fuse and we are back to fuse 8 controlling the lights. oh man this is confusing