Intermittent low voltage while running - Page 3 - Hyundai Forums : Hyundai Forum
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post #21 of 30 (permalink) Old 03-06-2019, 01:57 PM
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I've never heard of an alternator getting up to 19 volts before! How long does it stay up that high? I'm surprised it hasn't burnt out all your light bulbs.

Voltage is controlled by the alternator regulator, which is directed by the ECU as a result of input received from the battery sensor. You've replaced 2 of those 3 parts already. You've somewhat tackled possible grounding issues. Tricky problem you've got for sure! I applaud you on how much troubleshooting you've been able to do on your own.
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post #22 of 30 (permalink) Old 03-06-2019, 08:04 PM Thread Starter
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Quote:
Originally Posted by MaddMaverick View Post
Look on your negative battery terminal. Is there a little box with wires plugged into it? Mine is an 11 w/2.4l and has it.
Yes, the dealership replaced that sensor when I took it to them. I assumed it was that sensor as well but it didn't solve the issue.
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post #23 of 30 (permalink) Old 03-06-2019, 08:10 PM Thread Starter
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Originally Posted by CyprusCorner View Post
I've never heard of an alternator getting up to 19 volts before! How long does it stay up that high? I'm surprised it hasn't burnt out all your light bulbs.

Voltage is controlled by the alternator regulator, which is directed by the ECU as a result of input received from the battery sensor. You've replaced 2 of those 3 parts already. You've somewhat tackled possible grounding issues. Tricky problem you've got for sure! I applaud you on how much troubleshooting you've been able to do on your own.
It's been at high voltages twice, both times I was on the interstate (at rush hour) so I didn't feel comfortable pulling over immediately. First time it was high for maybe 7 minutes, second time maybe 2 minutes.

I don't know the exact mechanics of the voltage/alternator regulator that you mention, but I wouldn't think it would output 18-20 volts even if the ECU was calling for it. Which makes me wonder if it's a on/off switch (from the ECU) or is the ECU passing an exact voltage that should be attained. I don't know - and it's honestly hard to find information about the smart charging system.

I'm hoping it's not a bad ECU...
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post #24 of 30 (permalink) Old 03-07-2019, 11:54 AM
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An alternator can output quite a lot of power. It's not really voltage limited per say, as an alternator is a current generating device. it will generate current based on its duty cycle and RPM's to maintain a a voltage managed by the ECU/voltage regulator. Next time it happens, can you try turning on your rear defrosters? Those will use a lot of current, and should help bring your voltage down. I don't think it will help you diagnose the problem, but it will help save your other electronics!

Does anyone who knows more about cars know what other part of the car would measure the voltage of the vehicle? I presumed the voltage regulator both regulated and measured voltage, but I could be wrong!
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post #25 of 30 (permalink) Old 03-25-2019, 07:18 PM Thread Starter
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I wanted to give an update to this in case anyone runs into the same problem.

So I had the alternator replaced ~2-3 weeks ago. A couple of days later, I used my remote start to start the car (this is the OEM Hyundai Remote Start) - it didn't start so I knew something was up again. Now this behavior had been seen before along with the voltage issues that caused me to create this thread.

I had always written this off as the remote start using voltage to determine when the car had started or some fail safe, but the voltage on the battery was good at this point. Then I started to think about this post:

Quote:
Originally Posted by AUTOSPARK View Post
High resistance/open circuit on the alternator output.
What if the Remote Starter was the open circuit? The Remote Starter being a cause didn't even register as a cause for me but the more I thought about it, the timings of when the remote start didn't work and the voltage issues always seemed to match up.

After disconnecting/reconnecting the battery (the reset), I've been mainly just avoiding the remote start and the car has been working perfectly. I still want to cause the issue to happen again so I can find out what exactly on the remote start is to blame (the larger module or the DNA card/thingy) but the weather is getting better so I've been fine without it.

Another thing I noticed when the last issue came about (post-alternator), the voltage was dropping very slowly - like the new alternator had more power to overcome the open circuit.

If I find out what exactly is the culprit, I'll update this thread again but I'm almost positive it was something in the remote start circuitry. Thanks everyone!
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post #26 of 30 (permalink) Old 04-04-2019, 12:01 AM
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How reliable is your USB volt meter? Is it Made in China from ebay or something?
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post #27 of 30 (permalink) Old 04-04-2019, 08:01 AM
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Huundai battery cable clamps are really poor and have trouble tightening enough to make good contact on a lot of batteries. I know this is very basic. but make sure they are tight.The nut gets tight before the ckamp is tight enough. Wiggle the clamp by hand to check I have the auto store lead caps on my posts to get a tight fit. When you read high voltage it made me think the alternator was running without a battery across the output, as in bad connection. That and the bad ground contacts to the car body are well known priblems. It looks like the dealer took care of the grounding problem.

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post #28 of 30 (permalink) Old 04-04-2019, 08:26 AM
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North American Battery Posts are Smaller

After I replaced my battery, I too found that I could not get a tight clamp on the positive battery post.

The batteries available here have a slightly smaller post diameter than the original Korean posts, so you can't tighten the clamp enough.

I removed the nut from the positive clamp, and added 2 small washers under the nut.

That provided enough additional force to tighten the clamp to the post and make the connection solid.

Worth a try.

Last edited by M in Toronto; 04-04-2019 at 08:31 AM.
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post #29 of 30 (permalink) Old 04-04-2019, 08:55 AM
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I have taken a large socket, put it on top of the clamps, and lightly tapped the clamps down on the battery posts before tightening the hardware. Make sure there isn't stray material at the top of the opening on the clamps that might make it harder to get them fully seated on the posts.
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post #30 of 30 (permalink) Old 04-23-2019, 09:05 PM Thread Starter
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Quote:
Originally Posted by AUTOSPARK View Post
High resistance/open circuit on the alternator output.

I assume the battery warning light is remaining off which suggests the alternator is actually generating voltage. That voltage just isn't getting to the battery. When the fault is present measure the voltage right at the alternator output and compare the voltage there to what's displayed on your USB charger. If the voltage at the alternator is significantly higher than that displayed on the USB charger that confirms there is a problem somewhere in the alternator output circuit.
Quote:
Originally Posted by lafetoo View Post
How reliable is your USB volt meter? Is it Made in China from ebay or something?
It was from amazon so fairly cheap but the low voltage was verified with a external battery charger, not to mention the car dying because of insufficient power. The USB meter may be inaccurate but it's just backing up feedback that I already know existed.

I stopped using the remote starter and the issue is completely gone. From 1-2 times per week (towards the end) to a completely fixed car.
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