The last 2 days of driving my Ultraguage shows that my voltage is dropping to 12.8v and bouncing around up to 13.8 or so and back down. This went on for 30 miles or so and then back up to a steady 14.17v where it normally runs for about 20 miles to home. Yesterday it happened again for a few miles and then pegged to 14.17 for the last 50 miles or so. What could be failing like this and then returning to normal? I guess it could be the UG. Other than that what should I look for, test, anticipate etc.?
Voltage fluctuation 2012 Elantra
- Thread starter schuylkill
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How long have you had an UG and how long have you been watching voltage? It may be normal. Many newer vehicles the voltage regulator is under engine computer control and it will back it down as a fuel saving measure when full output is not required.
I've had an UG in this car for several years and this is not normal, something is up.
Then I would agree with Rand. Likely worn brushes.
I'd assume a bad connection somewhere from alterntor to battery, or battery to engine, or ECM to voltage regulator in alternator, or the voltage sense line to alternator, if one exists.
Alternator brushes, on a 2012 would be way down on my list of fluctuating voltage culprits.
A failing battery is not going to accept 50 amps one second and then 10 amps the next which would be required to have voltage rapidly fluctuate as reported.
Almost all weird electrical issues are bad electrical connections somewhere, and most everybody looks at them and decides they are 'just fine'
'just fine' one second, magic smoke genie released the next.
Alternator brushes, on a 2012 would be way down on my list of fluctuating voltage culprits.
A failing battery is not going to accept 50 amps one second and then 10 amps the next which would be required to have voltage rapidly fluctuate as reported.
Almost all weird electrical issues are bad electrical connections somewhere, and most everybody looks at them and decides they are 'just fine'
'just fine' one second, magic smoke genie released the next.
Nick1994
$100 site donor 2024
My Sonata does smart charging. With my foot on the gas the voltage is low, when coasting it is high. I made a post about it last year with some videos. Is it like this?
https://www.bobistheoilguy.com/forums/ub...gin#Post4594405
https://www.bobistheoilguy.com/forums/ub...gin#Post4594405
Quote:
I'd assume a bad connection somewhere from alterntor to battery, or battery to engine, or ECM to voltage regulator in alternator, or the voltage sense line to alternator, if one exists.
The one problem I've had with this car, and it is since it was new, is supposedly an electrical ground problem. If I move the car a short distance and then turn it off, if it sits awhile, when I try to start it, it will turn over but not start. This will happen almost all of the time in this situation. Over at hyundai-forums.com there is a Hyundai dealer mechanic who says it is common on these cars and is a grounding problem. I've cleaned the paint from the grounding points as he suggests but it hasn't fixed the problem. Perhaps this voltage up and down is related, but why would it take 272K miles to show up? Maybe this is how it should behave and it is fixed? I hate electrical problems because I'm an idiot with electrical stuff.
I'd assume a bad connection somewhere from alterntor to battery, or battery to engine, or ECM to voltage regulator in alternator, or the voltage sense line to alternator, if one exists.
The one problem I've had with this car, and it is since it was new, is supposedly an electrical ground problem. If I move the car a short distance and then turn it off, if it sits awhile, when I try to start it, it will turn over but not start. This will happen almost all of the time in this situation. Over at hyundai-forums.com there is a Hyundai dealer mechanic who says it is common on these cars and is a grounding problem. I've cleaned the paint from the grounding points as he suggests but it hasn't fixed the problem. Perhaps this voltage up and down is related, but why would it take 272K miles to show up? Maybe this is how it should behave and it is fixed? I hate electrical problems because I'm an idiot with electrical stuff.
Since you think you have a problem (or are just concerned you might have one) go to first steps.
Check, clean, tighten all electrical connections involved in the charge circuit. While you are there do the same on the starter circuit.
A "ground problem" is not necessarily limited to the battery to frame (or engine) ground point. Battery voltage moves from the negative terminal to the positive terminal (perhaps unintuitively) but that means the return point is the positive wiring. People tend to think in terms of the opposite when trying to figure out automotive electrics in their heads.
Take the battery to a known good shop and have them do a load test.
Next comes alternator. It is a wear item, so it's not unusual to have progressive failure. Also, the voltage regulator is operating under severe service conditions; that isn't a measure of how you drive, it's a measure of the job it's required to do and it's high electronic stress even when operating perfectly. So regulator failure is common and taken over x number of units, inevitable in some.
The problem there is Removal & Replace (R&R) of the alternator itself. I am not familiar with your particular vehicle so maybe this isn't an issue, but a friend has a Hyundai Tucson and alternator R&R required going in through the passenger wheel well, including strut removal. An alternator can be load tested at most chain type auto parts stores for free, but that doesn't help the R&R issue or rate hours. If you can't tackle the job yourself you may as well replace the alternator since the added cost won't be much in comparison to your labour bill.
Check, clean, tighten all electrical connections involved in the charge circuit. While you are there do the same on the starter circuit.
A "ground problem" is not necessarily limited to the battery to frame (or engine) ground point. Battery voltage moves from the negative terminal to the positive terminal (perhaps unintuitively) but that means the return point is the positive wiring. People tend to think in terms of the opposite when trying to figure out automotive electrics in their heads.
Take the battery to a known good shop and have them do a load test.
Next comes alternator. It is a wear item, so it's not unusual to have progressive failure. Also, the voltage regulator is operating under severe service conditions; that isn't a measure of how you drive, it's a measure of the job it's required to do and it's high electronic stress even when operating perfectly. So regulator failure is common and taken over x number of units, inevitable in some.
The problem there is Removal & Replace (R&R) of the alternator itself. I am not familiar with your particular vehicle so maybe this isn't an issue, but a friend has a Hyundai Tucson and alternator R&R required going in through the passenger wheel well, including strut removal. An alternator can be load tested at most chain type auto parts stores for free, but that doesn't help the R&R issue or rate hours. If you can't tackle the job yourself you may as well replace the alternator since the added cost won't be much in comparison to your labour bill.
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