Continuity between pos and neg battery terminals - Ford Powerstroke Diesel Forum
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Old 04-24-2012, 02:18 PM
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Continuity between pos and neg battery terminals

My batteries would die in like 4 min. so i checked and had continuity between both battery terminals. I isolated the problem by eliminating items from the loop one at a time and rechecking the continuity. I eliminated the alternator and starter, then went to relay on the fender and found the glow plug relay was shorted out. ( Replaced glow plug relay ) and had no continuity. I thought i was done. so to be a little anal i checked the continuity as i was hooking things back into place and the fuse box under the hood is grounding out! So i unhooked the pos lead to the box ( to test easier ) i unpluged one relay at a time to see if any had shorted out and came up with nothing, the box is still grounding out. Sorry for the long post, Any suggestions on where to look next?
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Old 04-24-2012, 03:18 PM
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I'm not clear on what you're saying....

You have current flow? Draw from the battery if you connect a meter in series between the post and cable end of either terminal? (I wouldn't call that continuity between pos/neg)

In any event, if a draw is what you're seeing, you're actually supposed to - at all times to keep the computers "alive". And what do you mean by the "box is still grounding out"? It's plastic - isn't it? Are you sure you even have a problem? Could you just have a battery problem?

First thing I would do is to remove the batteries, charge them up fully, and take them somewhere to be individually Load Tested at a High Rate (not the 100A cheapies the kids want to use at the Auto Parts stores, you should load them at 2 or 3X times that because they're HiCap batteries)
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Old 04-24-2012, 03:31 PM
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Sorry no i had a dead short that killed both batteries in like 4 min, and when tracing main wires to see what might be grounding out i found the glow plug relay was bad i replaced it and still have the batteries out of truck. i did have them checked and i only go to a local battery dealer to do it right. before hooking the batteries back in i ohmed the pos wire and the frame and it still seemed to be grounding out somwhere. and you are right the housing is plastic... lol the pos stud on the box ( without the wire hooked to the stud coming from the relay on the pass fender) ohms to the frame , so does that mean it is still grounding out somewhere? i dont want to hook everthing back up until i find out what may be grounding out still. if i hook the power wire back in to the fuse box, and i take my meter and set it to ohms ground lead to frame and pos lead to ground cable it ohms out. when i put pos lead to pos battery cable it ohms out! so i would think that something is still shorting out somewhere?

Last edited by Deere1200; 04-24-2012 at 03:42 PM. Reason: forgot some stuff
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Old 04-24-2012, 04:00 PM
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I would go by the spark you get when reconnecting the battery. You Will see some spark, as I said there's always some draw (more at first) but, anything that would kill a charged battery that quickly (like the almost 200A load of the Glow Plugs) would look like an arc welder when connected, I'd think it would be obvious.

Give it a try, I think the continuity you're seeing sounds normal to me, a bulbs filament or any of the electronics would account for some. If you don't get a tremendous spark, then you could measure the draw by putting the meter in the Amps position and connect only one battery with the meter in series between the post and cable. It might be a few Amps at first, but then over 20mins or so drop below 1 Amp (with No Lights or anything else On)
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Old 04-24-2012, 04:15 PM
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when the cables are hooked up i agree the computer is going to draw some, they all do on the newer stuff. but it is acting like a dead short, and i dont think that the possitive battery cable ( unhooked from the battery ) should be grounding out on the frame? So that is why i am leary on hooking everything back up
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Old 04-24-2012, 04:32 PM
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Here's what we do on AC electronics, use a bulb to connect the power through. If you had any headlight bulb around, use It between the post & cable. It will limit the amount of current that can be taken to ground. If the headlight comes on as bright as it would as if you connected it + to - Then you know you've got a pretty high draw and something Is wrong. I would think, if all is OK you should see either no light at all or a very dull orange. If so, I think it would be safe to connect your battery....
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Old 04-24-2012, 04:32 PM
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How many ohms do you measure between the positive and negative cables?
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Old 04-24-2012, 04:37 PM
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i will give that a try, this all started with me hauling hay home and an hour after getin home i had no power anywhere, the batts tested at like 1 v each. i found the short to be the glow plug relay. and now just dont want any more problems! i just didnt think it should be givin me a reading when i hook the meter up that way! rackin my brain
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Old 04-24-2012, 04:38 PM
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i didnt check the ohms on the negative when it beeped. but the positive i got like 3 when i ohmed it to the frame ground
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Old 04-24-2012, 08:13 PM
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Well, I sat back had a beer, went to shop and looked at things. I tried what you said and in fact it worked with light real dim. So then i realized i was overthinking the problem. Hooked everything back up and all is well. Chargin good !! I am sure it was the beer!!!! Not , but it helped... And thank you for the info NoRalPh!!
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