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Electrical problem need diagnsis

We have a 2006 Toyota Sienna Mini-van that was new to us when we bought it last October. A few months after we bought the car, we were surprised to discover that it appeared to have a dead battery one morning. Wouldn’t turn over, made no noise, just dead. We blamed it on a possible interior light left on by one of the grandkids, but weren’t sure about this. The car ran fine after a jump and continued to do so for weeks after this. The the problem occurred again with the same ambiguous circumstances. Another jump an no problems again for more than a month. Then it went dead in a parking lot while we were in a store - so was dead after only 20-30 minutes. Unfortunately, a grandkid was in the vehicle running something off the power outlet (a phone?). A jump worked again and no problem for an extended period of time.

This summer we took a road trip from our home in northern Minnesota across North Dakota and Montana to Glacier National Park. On the way across North Dakota we stopped for lunch at a information/rest area in North Dakota. After finishing lunch (20-25 minutes), we found the car “dead” again. An attendant at the rest area gave us a jump and we headed to a Wal-Mart (it was Sunday) in the next larger town. They checked the battery and said it appeared to be fine. They didn’t have the capacity to check the alternator or other electrical related stuff. We continued on to Montana and had no further problems for a few days. Then one morning it failed to have any battery power and we needed a jump from someone in the campground. We headed to a repair shop that handled electrical work about 50 miles away.

The repair shop confirmed that the batter seemed fine, but found the output from the alternator was not as expected when running the car. They recommended replacing the alternator. After replacing the alternator we returned to our trip and things were fine for two days. Then the car was dead again. After a jump we headed for an auto parts store and bought a quick jump unit so that we would no longer need to rely on others and vowed to get the car fixed when we returned home.

On the way home, stopped at a rest area to have lunch and the car “died” again in the few minutes we spent having lunch. The jump starter worked fine and we continued on. We needed another jump later in the trip home, but the pattern of working a couple of days and then failing continued. Since returning home (over a week now), there hasn’t been any problem. The car was used on one long days driving (about 8 hours of total driving) and other wise short trips around town.

The unpredictable nature of this problem and the disappearance of the problem after getting a jump and driving has us stumped. The car acts as though the battery is getting charged after the jump, but at some point loses it all and in some cases this happens in less than 1/2 an hour although we don’t know for sure that the battery was fully charged when we stopped. I suppose it could be barely charged when we stop and in 20 minutes loses what is left. But often times, like now, the battery seems to remain charged for days. In the past it would be okay for weeks.

The car has power seats, power windows, power locks via a key fob, power sliding side doors and a power back hatch door. On the camping trip these power doors were used frequently as we would get things out of the car or put them back in, but that was going on every day and the power would disappear after 2-3 days rather than 20 minutes.

At this point we can’t duplicate the problem at will. We have to wait for it to happen. Then a jump start and driving restores the power for as much as 1 or 2 days, so getting to the repair shop immediately after it happens isn’t very useful. Leaving it at the repair shop for days hoping it will happen while there is also impractical since we really depend on the car.

Any ideas as to what could cause this “strange” problem? We will be taking it in for repair at an automotive electrical repair shop in a few days, but I would like to have some idea of what they can or should be looking for. Thanks for any ideas.

If there was something in the vehicle that would drain the battery in 20 minutes, it would either blow a fuse or I think the car would be burned to a cinder. I wonder if the battery has a shorted cell. This is the one component that you didn’t replace and I am not sure what is meant by “the battery appears to be fine”. I don’t like to throw parts at a problem, but in this case, I would try a new battery.

A new battery may be in order, but if you choose not to replace it (or if the problem persists after replacement) I recommend you carry around with you a portable jump starter. This is a klutzy workaround, true, but if the shop cannot give you relief at least you will never be stranded.

Here’s a link to some starters:

You do need a battery. Batteries can develop an intermittant internal short, especially when they get a few years old. If it shorts internally while driving,especially at high speeds, it can damage the alternator. Its not worth messing with, not for the cost of a new battery.

Have both battery connections (cables) been removed and the cables and the battery posts cleaned? When this problems occurs, will the headlights still work? Or is everything in the car stone dead?

A battery with a “shorted” cell presents you with a 10 volt battery that will TRY to crank the engine but seldom succeeds. This condition seldom if ever goes away with a jump-start. A battery test will spot it instantly. A battery with an open cell connector, (the opposite of a short) will produce zero voltage and will not be cured with a jump-start…Have the battery load-tested by someone who knows what they are doing…Wall-Mart would not be my first choice…

I would also check the other ends of both the battery cables to be sure that they are securely connected to wherever they go…

In all the checks done, was the battery ever disconnected and reconnected? I’m wondering if the wire connectors are just a bit loose.

Sorry for the delay in getting back to this. Have been busy with responsibilities away from the computer.
Both the Wal-Mart and auto repair shop ran “tests” on the battery using their machine to see what voltage it was putting out. Both described the battery as having plenty of power in the test. The posts were checked and cleaned and small bolts attaching the cables to the posts were replaced by the auto repair shop, so the battery was disconnected and reconnected at some point by them. They also made sure the connections were tight.
We are now carrying around a portable jump starter and it works fine when needed. We have been home for over a week now and the problem has not occurred again. I’m wondering if there was something about the sustained driving we did each day that contributed. I have no idea what this could be, but it is strange that it was happening every couple of days on the trip, but not once since returning to the normal driving routine.
An internal short in the battery is something possible I suppose, but I don’t know why it would come and go with such strange frequency (present while driving most of the day, not present when drives are relatively short and occur at irregular intervals). That is something for the repair shop to address I guess. We could just replace the battery and wait and see I suppose, but it is bothersome not knowing what is going on and when it will happen again.
Thanks for the input.

In the normal charge and discharge cycles of a battery, the plates inside build up layers of scale. The scale can and will flake off and when it does it can short out tow or more plates. Modern batteries use plastic grids to try to keep this from happening, and they do work. Batteries last a lot longer now than they used to, even with the higher demands that modern vehicles place on them.

Most of the time, the scale will settle to the bottom where the grids keep them out of harms way, but they can float above the plates. Above the plates, they get jostled around, thus it becomes an intermittent problem.

I don’t see why you are so willing to buy a portable jump starter and a new alternator but so resistant to buying a new battery. If I have a battery that is 4 years old or older, the first time it doesn’t start the car, it gets replaced that day.

If your battery has the removable cell covers, pry them up and look inside. If you don’t see nice clean edges on the tops of the plates, then that battery is done for.

It does sound like a short, either internal to the battery or in the wiring somewhere. Since it is a new car, the battery does seem more likely (I had a 80’s Volvo with similar issues and after throwing money at it, found that some of the wiring casing had degraded and all it took was a little electrical tape.)

Like others have said, this might be a bad battery. Batteries can become intermittant like any other electrical componenent. That isn’t their normal failure mode, but it can happen. And like any intermittant problem, it is not possible usually for a repair shop to diagnose the problem unless they have access to the vehicle when it isn’t working. You may have to have it towed to a repair shop the next time it fails. Or take it to the repair shop when it is working and ask them to start it up several times a day until it fails. In the meantime, you’ll have to rent a car. Week rentals with unlimited mileage aren’t usually that expensive if you schedule them in advance.

It could be a host of other things too. Alternators can be intermittant. As can most any electrical part.

I guess if this were my problem the first thing I’d do it remove the battery from the car and take it up to Sears (or most any big-box auto repair place) and have them charge it up and do a load test on it. Assuming they said it was “good”, I’d reinstall the battery, and drive the car as I normally would, checking the alternator voltage (to spec) each time I started it up, and each time I stopped the engine. I might even put my volt meter on the passenger seat and run some fused test wiring to monitor the battery voltage and the charging voltage as I drove around doing my daily errands. Only try this if you are trained in and very experienced with auto electrical system diagnostic procedures and repair though, as doing it wrong could cause a short and possibly start a fire. One idea would be to ask your electrical-mechanic to set you up with a battery monitoring system. Probably the best idea to get your car back on the road and reliable to drive is to take your car to the shop and have them keep it there until it fails. You can use this as an opportunity to try out a newer car as a rental for a week.

Rental car for a week vs new battery, come on.

I will add that a relay may be closing and powering up a significant load such as the fuel pump. Such a problem is rare but it has been found to be the problem more than once in recent years.

Just a comment. I brought a one year old battery back to Walmart for exchange. It was in a car that sat most of the time. The battery was so shot that it wouldn’t crank the starter and wouldn’t take a charge. The Walmart guys said it was fine but finally gave me a new battery. I just don’t put much stock in them. So its either your battery, alternator not putting out enough at speed, or a parasitic drain.