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Intermittent loss of battery power

In my 2004 Honda Civic I have a strange recurring problem for almost a year that I haven’t been able to nail down. Maybe a couple times a week on average I lose battery power when the car is off - there is no power when I turn the key, lights don’t work, etc. I have a new battery and have had the charging and starting systems tested (incidentally the shop was unable to replicate the problem while they had the car so didn’t know what else to do) so that’s not the problem. Just to clarify, this is not a problem where the power comes on when I turn the key to the “on” position but the engine won’t turn; I simply have no electrical power at all - no dash lights, no power to door locks, radio requires resetting when power is restored, etc. And when the engine turns it turns strong - it’s not a weak current; it’s simply on or off.

I’ve checked the fuses and all seem fine. I’ve cleaned the battery terminals and they don’t show any sign of corrosion or build up that would suggest something wrong with the battery cable.

The two clues I get are that this seems to happen when the temperature is low - for a while the problem would ONLY happen late at night and into the early morning, and by midmorning having sat in the sun the car would start fine (it almost seemed that about 55 degrees was the cutoff - if it got colder than that the car would not start in the morning, but if it didn’t drop below that at night it would start). The second clue I get is that when it won’t start, if I wiggle and press on the battery fuse in the fusebox and grab and wiggle the bundle of wires leading away from the positive terminal of the batter at various points, I can almost always get power restored - though I haven’t been able to get any one method or any one location to work with sufficient consistentcy to say it’s the silver bullet.

Any ideas? The mechanic said there’s a possibility with temperature variations you could get changes in resistence that might affect power delivery along the cable, but again with no evidence of corrosion and the fact that I never get weak current or engine turnover - it’s simply the current is on or its off - I wanted to ask for some more ideas before changing the cables. I figured fuses are either good or blown; you wouldn’t get power sometimes from a blown fuse, but is it possible to have a partially blown one or a broken one that with some manual manipulation restores contact or contracts with cold and breaks the circuit?

I’ve cleaned the battery terminals

Did you check both ends of each cable? Have you tried wiggling the cables while it is not working?

Note: cables can go bad internally, thus the wiggling of the cables suggestion.

A defective (but not blown) fuse is certainly possible. Also possible would be loose contacts on the fuse holder or a loose wire connection somewhere nearby. It might not be a main power wire, but instead it could be one of the smaller ones. (If you can’t get power to the circuits that energize the relays for the heavy loads like the starter, then it doesn’t matter if the heavy wires are okay or not.)

You may need a better mechanic. You will have to leave the car overnight with them when the temperature is low so that they can measure voltages while the problem is present.

I don’t think measuring battery voltage is going to tell you a thing. I think this is a voltage/ no voltage problem and my first suspect would be the cables and their connections (both ends).
The next time it happens, If you have a decent set of jumper cables try hooking a cable from the ground post of the battery in such a way that the jumper is digging into the top of the post and not just the outside of the terminal and the other end to ground on the engine.If that doesn’t do it try jumping the positive post to the cable terminal on the starter that the heavy wire gos to. Hook up the starter end first.

Measuring the voltages at each end of the cables when the defect is present most certainly will tell you something.

Could very well be a bad gnd from the battery to the chasis or just a bad ignition key switch. Cold makes things shrink and this could be causing just enough of a connection problem.

If you haven’t done so, check the ground wire (the black wire from the battery) and make sure that its far end is solidly attached and not corroded. It’s very unlikely that it is your problem, but if it is, you can spend months looking at other stuff.

Go to your local Radio Shack or parts store or Cheap East Asian Stuff R Us and buy the cheapest analog voltmeter they have in stock. Next time your power goes on vacation, set the meter to the lowest scale greater than 12 volts, jam the black probe onto your negative battery terminal and start down the red wires measuring DC volts with the red probe wherever you can find metal to measure at. Presumably, you will eventually find a place where the 12 volts is gone. The open circuit is someplace between that point and the last place you found power.

Though it isn’t likely there may be a problem with the battery internally. There may be a bad post connection. You can see if you have voltage at the battery posts using a test light probe when the trouble happens. If the battery is ok then check for a bad connection to the main panel under the hood from the battery. You should have power going to the panel at all times.


Thanks to all the useful tips below. I finally discovered what it was - the fuse was broken along one end where it joins the contacts inside the casing (but not burnt out). Because the battery fuse is a screw-down type though, it was holding everything in place so I couldn’t see the breakline until I removed the fuse and slightly twisted it, which is when I saw it separate from the contact. The clue I got was very faint arcing was visible inside the fuse one night when I happened to be on a dark street and I had the fusebox open and was wiggling the fuse while pressing the keychain doorlock to be able to tell when power was restored. The break explains why sometimes I’d draw no power from the battery, but wiggling it would be just enough to reestablish contact and close the circuit, “fixing” the problem.

Thanks again for all the suggestions.

Glad you found the trouble. Thanks for the update.