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2011 Hyundai Sonata won't start, no electrical

My wifes 2011 Hyundai Sonata would not start yesterday at the clinic. I purchased a new battery went there today to replace the battery. Before I started the work I tried starting the car. When I turned the key to the on position the radio came on and the dashboard lit up like normal. As soon as I turned the key to start the car the battery went completely dead. The starter did not engage and the electrical went out.

I replaced the battery. When I turned the key to the on position nothing turned on. Not the radio or any of the dashboard lights. I tried starting the car and there was not response, exactly like a dead battery. I purchased a new battery and they tested it right in front of me before giving it to me so I feel like I can rule out the battery.

I double checked that he connections were tight. I tried jiggling the shifter, pushing the brake pedal, jigging the steering wheel around, jiggling the key in the ignition. The positive battery terminal connector has a fuse, it appears to be intact. I also checked the fuse panel in the engine compartment. All of the large fuses are intact (I only looked at the 3 or 4 of the large ones that were visible from the top). I didn’t check the smaller fuses, I wasn’t sure which ones to check.

A little background;
For a couple days in a row my wife was noticing that the car was struggling to start (she didn’t mention this to me right away). I noticed that when we were driving it the head lights had a very suttle flicker. When were idling at a stoplight it appeared as if the lights were dimming and getting brighter rapidly. I noticed it from the reflection of a license plate and dismissed it as maybe just the wind causing the license plate on the car ahead of us to wobble. It was suttle and not very pronounced. Yesterday my wife went to the clinic and when she was leaving the car would not start. Someone helped her with jumper cables but she was not able to get it started. Even after letting it sit for 5 minutes before trying to start it.

My buddy thinks it’s the ignition switch itself, but that sounds quite a bit beyond my capacity.

I suspected that since the lights were fluttering/dimming that it was an alternator problem. Even if the alternator is bad wouldn’t the car still run on a fresh battery?

Can anyone suggest some other troubleshooting steps? Any ideas what the issue could be?

Please help!!!

Battery cables have connections at both ends that need to be checked for cleanliness and tightness.

It sounds like a textbook corroded connection on the battery cables. As NYBo said, it could be on the non-battery end, but that is less common. If you don’t have a multimeter, I can’t recommend any ‘safe’ troubleshooting procedures other than removing and thoroughly cleaning and retightening the connections.

On a 2011 it is unlikely to be the battery or any other major component. Yes, the car should at least start on a fresh battery with a bad alternator.

Power from the battery needs to be supplied to the power panel under the hood which distributes power to the whole car. The lead from the battery to that panel may have a bad connection. This would make it seem like the battery is dead but it really isn’t. You would be wise in investing in a voltmeter so you can check things out and see where voltage is getting to. In this case you would need to check the power while trying to start the car or with a good load on line. From the other things you stated about the lights flickering it appears the alternator has some bad diodes inside it. You can have a load test done to check that out.

Is this car still under warranty?

I would not assume anything with the fuses. Check the main power fuse with a multimeter. Also, you didn’t hook up the battery backwards did you? On my car, I need to make sure the positive a negative posts are on the correct sides, because my battery size is made with one model positive on right, the other positive on left.

It should be under warranty. Here is the schematic and I would swap the Start 1 relay after checking all my connections.

Thanks for all the suggestions. I have a multi-meter. I mostly use it for doing wiring around the house so I don’t have much experience using it on cars. When you say to check the main power fuse, how would I do that? Is the main power fuse the one positive batter wire?

The warranty period was up about 6K miles ago.

My next steps are to head out there and inspect the grounding cable. Make sure it’s secure to the body. Also I’m going to have the battery tested at a different auto parts store. I don’t have anyone to help me until later so I won’t be able to test the voltage while starting the car.

The old battery read 12 volts with the multi-meter. I put it in my other car and it started right up. With the battery ruled out I’m on going to disconnect the ground in the engine compartment, clean it up and re-attach it and go from there.

The ground cable on the car side did not appear to be corroded and the wire didn’t have any visible corrosion. I still disconnected it, scraped up the metal on the car side and the plate at the end of the ground cable, added dielectric grease to all the connections. The car started right up. I swapped out the new battery with the old battery and it started right up. Everything seems to be working great now. I’m hoping that was the cause.

The main power fuse should be located inside the main distribution panel under the hood. It will be at least a 80 amp fuse, probably more. The trouble you had could have been due to a faulty ground but I would guess it really was with the power input side. If the trouble returns use your meter to check for voltage drops beyond the battery connections while there is a good load on the battery. Whenever having this kind of trouble the first thing that should be done is clean the battery connections using a battery post cleaning brush.

My Corolla has 3 special type of high current fuses right near the battery. Fusible links I think they are called. Check if your car has this type of fuse, if so perhaps one or more has blown. In any event when you install a new and fully charged battery and even the dome light doesn’t come on when you open the door, that should be fairly easy to diagnose for an auto tech trained in electrical diagnosis. It’ll probably turn out to be something simple.