tcw0313 Posted March 7, 2013 Share Posted March 7, 2013 I have been searching all over this great site and a few others.. I am picking up my first MJ in a couple months as soon as I finish my current over seas deployment. This thing is perfect!! only rust that can be found is under the rear fender flair. No i have not checked the inside of the floor pans yet but from under there is no evidence of rust at all. I think almost too good to be true. Runs great with like 120k on milage.. But.... Last owner told me he had to install a quick disconnect on the battery terminal becuase of a short somewhere. its been a few years since i have had a jeep. is there a quick way to trouble shoot electrical? i know to check each fuse block with a multi meter and to check the grounds to the frame for any corrosion. but out side of that ? anyone have any ideas? Link to comment Share on other sites More sharing options...
jimoshel Posted March 7, 2013 Share Posted March 7, 2013 There are several ways but the way I prefer is to install a amp meter in one of the battery leads. Check the currant draw. Now go to the fuse panel and start pulling fuses, CB'S. Start with the big ones first. After narrowing it down to a , hopefully, single circuit it's just basic trouble shooting. Normally for a short it's a bad component. If not then the wiring has rubbed against something, wearing thru the insulation. Finding a short, especially an intermittent one can be one of the most frustrating jobs on a vehicle and when found will be so simple you'll wonder why it took so long. Good luck. Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted March 7, 2013 Share Posted March 7, 2013 Finding a short, especially an intermittent one can be one of the most frustrating jobs on a vehicle and when found will be so simple you'll wonder why it took so long. Good luck. Truer words have never been spoken. By the way, a common place for a short ot occur is at the very front of the intake manifold. There is a small group of wires that run down to the Coolant temp sensor (CTS), Knock Sensor, and O2 sensor. Sometimes this cluster of wires is laid directly on the header pipe of the #1 cylinder, you might already know where this is going. Super heated header burns through electrical sheath and eventually melts down to bare wire causing all kinds of havoc. I am curious as to why the PO had to install a quick disconnect. :hmm: Did he give you any other details? Link to comment Share on other sites More sharing options...
Biotex Posted March 8, 2013 Share Posted March 8, 2013 Just to add to what has already been stated, is that the alternator has diodes inside. A diode electrically allows for current to only flow in one direction. In this case, it keeps the battery from discharging (backfeeding) through the alternator and to ground. This will slowly discharge your battery, and yet your alternator will still work as normal. Keep in mind that it is common for the diodes to go bad in alternators. So if pulling the fuses one at a time doesn't find the problem, try disconnecting the alternator also. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 8, 2013 Share Posted March 8, 2013 off running the battery down is called a "draw", not a short. Easy to find. Link to comment Share on other sites More sharing options...
jimoshel Posted March 8, 2013 Share Posted March 8, 2013 A short in the wiring, or component will draw the battery down. Nit picking. Link to comment Share on other sites More sharing options...
Biotex Posted March 8, 2013 Share Posted March 8, 2013 A short is considered a negative to a positive, and will either blow a fuse, (trip a breaker), or melt the wire. Once the wire melts, it opens (electricaly speaking) at which point it is no longer a short. If the wire is large enough that it won't melt, then it will likely destroy the battery. So I see no way a short will drain a battery on a continuing basis. If I'm wrong here, please explain. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 8, 2013 Share Posted March 8, 2013 A short is considered a negative to a positive, and will either blow a fuse, (trip a breaker), or melt the wire. Once the wire melts, it opens (electricaly speaking) at which point it is no longer a short. If the wire is large enough that it won't melt, then it will likely destroy the battery. So I see no way a short will drain a battery on a continuing basis. If I'm wrong here, please explain. You are correct. Hence, Post #5. Link to comment Share on other sites More sharing options...
jimoshel Posted March 8, 2013 Share Posted March 8, 2013 off running the battery down is called a "draw", not a short. Easy to find. A short is considered a negative to a positive, and will either blow a fuse, (trip a breaker), or melt the wire. Once the wire melts, it opens (electricaly speaking) at which point it is no longer a short. If the wire is large enough that it won't melt, then it will likely destroy the battery. So I see no way a short will drain a battery on a continuing basis. If I'm wrong here, please explain. Both of these statements are of course correct. How ever when some poor slob goes out of a morning expecting to start his vehicle and go to work, or where ever and all he gets is 'click' if that I don't think he really cares much for the 'correct details' as to why. He just knows he's stuck with a dead battery. I still say nit pickin. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 8, 2013 Share Posted March 8, 2013 Both of these statements are of course correct. How ever when some poor slob goes out of a morning expecting to start his vehicle and go to work, or where ever and all he gets is 'click' if that I don't think he really cares much for the 'correct details' as to why. He just knows he's stuck with a dead battery. I still say nit pickin. Part of the nit picken is to help him fix it. He needs to know how to find a draw. We KNOW he's only got a click! Link to comment Share on other sites More sharing options...
oldseddie Posted March 11, 2013 Share Posted March 11, 2013 We had a Cherokee in our shop which was involved in a buy back. It would be fine for days and then a load would present itself and drain the battery. Turned out to be a bad ECU. We left it in a stall with an amp meter between the battery and positive lead and kept a watch on it. Once the draw occurred it was just a matter of unplugging things until draw disappeared. Link to comment Share on other sites More sharing options...
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