Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

2014 Corolla - Bad Alternator or Bad Battery?

Good Afternoon,

I bought my 2014 Corolla new a little over 3 years ago. Yesterday, when I was leaving work to head home I went to start my car and I was just met with my starter making a loud buzzing noise. My lights in my car, car fob, and etune radio were all working properly, but the car was just not able to start! My coworker told me that he heard of a trick where if you knock on the starter with something while trying to start it, it might give it enough of a kick to get going. Whether or not it was coincidence, it did work.

I was able to drive home, about 15 minutes (still daylight, did not need car lights), with no trouble. When I got home I turned my car off and waited for a few seconds and tried to start again. It worked, but it sounded like it struggled. I did it one more time and it failed with that same noise again. I resolved that I would just go get a new battery in the morning.

In the morning, my car was able to start, albeit with some struggle again. I made it all the way to work, and over lunch I was able to start it again and drive it to AutoZone to have them test the battery\starter\alternator. They told me the battery was too depleted to test it, so I went across the street to Walmart and bought a new battery. After replacing it, the car started like a champ as expected, and I drove back to Autozone to have them test my alternator and starter. The starter came back good, but they said that there was a fault in the test with the alternator. I gave them my old battery and asked them to trickle charge and test it just to see if it happened to still be a good battery that was just losing charge, or if it really was just a dying battery.

I called Toyota to schedule an appointment for the alternator, but the service technician told me that if my battery light was not on in my dashboard then it most certainly was not the alternator and likely just a bad battery. He said that he had been there for over 5 years and he’s only ever seen a dozen of alternators replaced in Toyotas, all of them in much older models than my 2014. He told me that it’s possible the equipment at Autozone may not be reliable, and to drive my car over the next few days and see if the problem arises again.

What does the community here think it may be? Is it likely it was just a bad battery and the Toyota tech is right in that readings from Autozone’s equipment could be incorrect? It just seems to me like the readings they are testing for in their equipment are not that complicated and I don’t understand why Autozone’s equipment would just give a faulty reading just because, unless the equipment itself was faulty. On the other hand, when my car was started it was driving just fine. If the alternator was not working properly, and my battery was dead\dying, I would have expected my car to eventually lose power to the electrical components which it did not.

A battery can have a dead cell which makes it a 10 volt battery instead of a 12 volt battery…The lights, door locks, buzzers, radio all will still work on 10 volts. But when you try to start the engine, an event that puts a big load on the battery, the starter can not turn the engine over…Any decent repair shop can, in a few minutes, determine where the problem is…About half the time, the problem turns out to be dirty / corroded battery terminal connections which can produce “dead battery” symptoms…The car will not start but the lights will still work…

If I was standing in front of the car with a voltmeter I could answer your question in about 15 seconds. Car not running, battery voltage should be about 12.2 to 12.6 volts. If its drained it would be lower. Start the car, voltage at the battery terminals should rise because the alternator is charging. You should see 14 to 15 volts. If you see voltage at or lower than you tested with the car off (12.2 to 12.6 volts), the alternator is most likely bad and the car is running off the battery. But is could be a wiring issue, or a starter issue because you didn’t give us any voltage data in the post.

Oh, and stop letting the dimwits at Autozone test your 2 year old car. Its cost you a battery that probably didn’t need replacing only recharging. Let real technicians diagnose the actual issue rather than throwing parts at it.

It could have been a loose cable, or an undercharged or worn out battery, or the alternator (least likely). How many miles?

I don’t know exactly off the top of my head, but between 40k-45k

The original battery in your Corolla least three years old. It may have been its time. Take the old battery back to the store where you bought the new battery and get your trade-in credit. Since the car is now “starting like a champ” relax and drive on…

The Toyota tech was mistaken. There could be a bad diode in the alternator. That could drain the battery and not illuminate the battery light. This fits your symptoms.

[quote=“Mustangman, post:3, topic:96076, full:true”]Oh, and stop letting the dimwits at Autozone test your 2 year old car. Its cost you a battery that probably didn’t need replacing only recharging. Let real technicians diagnose the actual issue rather than throwing parts at it.
[/quote]Actually, the “dimwits” didn’t cost the OP a battery that probably didn’t need to be replaced. It was apparently the OP who decided to buy the battery (at a competitor, no less). The equipment we use is probably as sophisticated as what the dealership would use, and it walks the person using it through the proper steps. If the battery is too discharged to test, the meter will state that on the display.

[quote=“texases, post:4, topic:96076, full:true”]
It could have been a loose cable, or an undercharged or worn out battery, or the alternator (least likely). How many miles?
[/quote]I had a customer request a battery test because of poor starting. When I went to put the clamp on the positive cable end (battery still in the car), the cable came right off. The negative was equally loose; the hold-down was also missing. I cleaned and tightened the connections, and the battery, starter draw, and alternator tests were fine. I advised him to get a replacement hold-down as soon as possible.The customer said he had the engine replaced recently. I guess the shop wasn’t too careful that day.

I had no problem buying the battery from Walmart because their 90 return policy covers batteries, so if my old battery was still good then I could just have returned it.

I got off the phone with Autozone and they tested the battery, and it is bad. Getting a new one wasn’t a waste of money. I have a friend with a voltmeter who will bring it to work tomorrow and we will run our own diagnostic to see what the voltage readings are. I’ll update tomorrow with the results.

Plug in battery/charging system testers are about $10-15. Plug them in to the acc plug and it’ll tell you what the battery voltage is. Then start the car and it’ll tell you what the charging voltage is. Then you pretty well know. Since they started taking voltmeters out of cars now, I just keep one in each car to take a look once in a while.

I have a 24 year old Corolla and have battled this problem the entire life of the car. It’s a Corolla thing for some reason. Comes w/owning a Corolla. Unless you’ve been jump starting other cars, or receiving jump starts, very doubtful your alternator is to blame. Probably just your battery is done for, so replacing it was a good idea. Hopefully you got the right size --physical and cold start requirement – for you car.

What’s causing it, if it isn’t the battery? I’ve had the following problems over years, all contributing to this symptom

  • Battery connections corroded or not tight
  • Faulty clutch safety switch
  • Faulty starter motor solenoid contacts (this is the most common reason)
  • Faulty ignition switch
  • Edit: Here’s a weird one. The charging wire between the alternator and battery got eaten by battery acid., developed a high resistance.

The best way to diagnose the cause is to ask your shop to measure the voltages on both terminals of the starter motor during attempted cranking. They should both measure at least 10.5 volts. If they both do, then the starter motor is the problem. If not, well, it depends on what the measure what to do next.

One bit of advice: I wouldn’t use either Walmart or Autozone to diagnose or fix this kind of problem. Either use the Toyota dealership shop, or find a well-recommended local inde mechanic who specializes in Toyota or at least Asian cars. Best of luck.

Not a personal slam on you @NYBo, if you work at one of the parts chains, sorry. There are knowledgeable folks there but they are in the minority in my experience. The caliber of the counter people I’ve encountered at AutoZone, O’Reilly’s and others is not exactly stellar.

Maybe because a former brother-in-law worked at one of the chains altered my perceptions…:wink:

Final Update

I tested my alternator again today, and everything looks good. I was reading 13.6v when the car was started, which is where it should be. Looks like it was just a dead battery. Thanks for all of your input.

1 Like

George, are you sure this isn’t the fusible link having done its job… melted by a current surge?

Not a fusible link that time. That wire between the alternator and the battery had a factory splice in it, in the worst place possible, right in the middle of a thick wiring harness in the engine compartment under the air filter box. I had to “Sherlock” that wire clean through the wiring harness to find the problem splice. Had to unwrap the whole thing. It turned out the battery had a slight leak, and the wire on the + post of the battery was touching the top of the battery case & decanting battery acid a drip at a time into the middle of the wiring harness. Eventually – it probably took 6 months or more – the acid made its way to that splice, and promptly ate the solder.

I have a 2014 corolla and the battery just went dead. I have found when it turns cold which it did last night is when the battery usually dies. Apparently the battery was about 3 yrs old. I charged it and went to oriellys and they swapped me in a new 3 yr battery in about 5 minutes for $129. end of problem.

Great work, George. :relaxed:

1 Like

Man, talk about milking the cow.
Test my battery but I’ll buy it somewhere else.
Now charge and test my old battery that I’ve already replaced.
Now check my alternator even though I’m going elsewhere to get it changed.

But it’s not just AZ that’s getting the shaft-

I had no problem buying the battery from Walmart because their 90 return policy covers batteries, so if my old battery was still good then I could just have returned it.

The nerve of some people never seems to surprise me…

1 Like

Autozone offers those services free of charge and as a customer I have no obligation to purchase anything from them. Not like those employees are getting paid any more or less because I was keeping them busy for 5 minutes of their time. Maybe they should offer more competitive prices if they wanted me to buy a battery from them. I think Walmart will live if I were to return a battery that was used for <24 hours.

Someone really needs an attitude adjustment.

1 Like