2001 Nissan Altima and the Phantom Short

Last Friday my car was running fine. Went to whole foods market with my girlfriend and then drove across the street to Kroger to rent a movie. When we got back in the car 5-10 minutes later, it wouldn’t start. Headlights/etc were all off. Interior lights and buzzers came on but the engine wasn’t even trying to turn over. Tried to get a jump from someone but it wouldn’t take and I ended up getting a tow back to my apartment. Left town for thanksgiving and got back this weekend. I did some electrical measurements and found that the battery’s positive terminal was at same potential as the engine block. Disconnected and inspected the line to the ignition coil and afterward the short was gone but then came back 10 minutes later. Sunday I checked again and found that the short was apparently gone again so I left it hooked up to my girlfriend’s battery (with engine running) for about 6 minutes. The engine turned over the second time I tried and I was able to verify 14.25V from the alternator. Left it running with doors locked for about 30 minutes and when I came back to see if the battery had charged, I found that the engine had stalled out. Finally I jumped it again and was able to drive it to a mechanic which is where it now sits. After I parked it, I turned off the engine and verified that it would not start again on its own. I had a 65 month battery installed in Jun 2007 and had never needed a jump until now.

My suspicion is that something is shorting and pulling all the charge off my electrical system and that this caused it to stall when there was not enough juice to keep the spark plugs firing. Hayne’s manual indicates that the only things directly connected to the battery are the alternator and the starter motor so I suspect one of these could be creating a transient short but my knowledge is too primitive to know why this would happen. There is still water on all 6 cells so the battery isn’t totally ‘cooked’. I’m sure the mechanic will figure it out, but I’m interested to hear any theories.

Did you clean the battery terminals??? First thing I’d do. Make sure all connections are clean.

Battery terminals are pristine. Guess I forgot to mention that in my post.

I appreciate the response!

Also check that you have a good ground connection from the battery post to the engine. If you jumped the Altima correctly, you made your last connection with the ground clamp to somewhere on the engine to avoid a spark initiated battery explosion. In essence you would have jumped around a bad ground connection.

Let us know what they do find.

You are describing an “open”, not a “short.” These are two very different things.

Quoting my original post: “I did some electrical measurements and found that the battery’s positive terminal was at same potential as the engine block. Disconnected and inspected the line to the ignition coil and afterward the short was gone but then came back 10 minutes later.”

During the times when it was reading like there was a short between the positive terminal and the engine block, there was of course no potential difference between the positive and negative terminals of the battery (battery read 0V). At other times when the battery was reading a low voltage (like 9-10) as opposed to no voltage, I did verify that there was continuity from the negative terminal to the engine block.

With respect to the jumper cable connection, there really isn’t any good place to clamp the jumper cable to the engine block and since I have never seen a battery spark when hooking jumper cables up directly to the negative terminal I just connected the negative clamp directly to the negative terminal. I’d think that if the ‘ground’ connection was not present that I would simply have no circuit and nothing would work at all. I suppose it is possible that something I could not see is loose or corroded causing this to break, but that doesn’t at all explain [in my mind] why the battery would keep getting drained.

Thanks again for the response. I am a Georgia Tech electrical engineer, but I really feel like an idiot sometimes when it comes time to look under the hood.

Battery shorted internally, intermittently. Shake and pound on battery while reading attached volt meter.

Are you saying that I am describing an open or that Researcher is describing an open?

I am using the term ‘short’ to describe that the positive terminal is at the same potential as the engine block. (i.e. my multimeter’s continuity check mode beeps when I test between the batt (+) and the engine block)

Yeah, an intermittent internal battery short is definitely a possibility but I had kinda ruled this out just because the cells all had water on them and I figured that an internal short would have rather quickly boiled off all the water from the electrodes.

Hopefully this is the problem and the mechanic can just do a warranty replacement on the battery and I’ll be good to go. Out of curiosity, what would cause an intermittent internal battery short? I guess if the battery shorted while it was idling this could lead to the car stalling out because there would be no potential diff at the spark plugs, but I don’t understand why that wouldn’t trip a fuse or something when there is such a surge of current.

BTW tardis - Love the name!

Turns out that hellokit was absolutely right! The problem was an intermittent short in the battery and $62 later I’m back on the road!

Thanks for all the feedback =)