2012 Elantra battery running at 11.7 volts

Messages
328
Location
Pennsylvania
Driving home today and my battery light came on. I have an ultragauge and it showed 11.73 volts, held there pretty steady for about 15 mile ride home. The car starts up. Battery is about 2 years old I believe. Original alternator and voltage regulator, just passed 334K miles. Regulator is external on the alternator. How can I diagnose what is failing?
 

JHZR2

Staff member
Messages
44,542
Location
New Jersey
Definitely low. I'd want to know what your battery voltage is with the engine off... if it's in the 10v range, then the battery has a shorted cell and the alternator is unable to source the current that the battery is "burning" up. I'd suspect at the age you mention, it's more just some worn components. Is there a replaceable voltage regulator? That would be my first look.
 
Messages
35,859
Location
ME
There's a chance that an external regulator has a diagnostic method that full-fields the alternator so it could make 16 volts, proving which part is at fault. Dig up your repair manual.
 

schuylkill

Thread starter
Messages
328
Location
Pennsylvania
With engine off 12.3 volts. Checked battery negative to positive post on regulator with engine running and reads 11.7 volts. $200 for Denso alternator and $150 for regulator at Rock Auto. Denso at NAPA is $378. What to do what to do. Could it be the brushes in the regulator are worn?
 
Messages
11,938
Location
North Carolina
I would unhook the battery cables and charge it. See what it will charge to. And see if it will hold that charge overnight. If it will hold a 12.6 overnight disconnected from the car , then i think you will need an alternator.
 
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14,996
Location
NE,Ohio
most likely the alternator.. just get a new one with internal regulator for 105, or the new denso(includes regulator) for 199
 

schuylkill

Thread starter
Messages
328
Location
Pennsylvania
Good news is on Rock Auto states regulator is internal so would only need to purchase alternator. Remy rebuilt is $135 think I may pull trigger on it depending on shipping cost and time, still looking into AA deals. Regulator looks to be external and it can be bought separately but is included with alternator purchase.
 
Messages
11,938
Location
North Carolina
Originally Posted by schuylkill
Good news is on Rock Auto states regulator is internal so would only need to purchase alternator. Remy rebuilt is $135 think I may pull trigger on it depending on shipping cost and time, still looking into AA deals. Regulator looks to be external and it can be bought separately but is included with alternator purchase.
The alternator is $185, plus shipping to you. core is $50 and if i'm not mistaken, you pay to ship the core back to them. So its more that $135 depending on the ship to you cost and the core shipping cost.
 
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Messages
679
Location
Minnesota
I bought a used OEM alternator for $25 for my 05 Accord about a year ago. Works great and was cheap. I'd say there is a good chance it will outlive a rebuilt china one. Found it on car-part.com at a local salvage yard.
 
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910
Location
PA
Isn't the best alternator a rebuilt one from a local alternator/starter service shop? I hear they often replace components with parts that are higher quality than the originals. Maybe this isn't true for all shops.
 
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4,639
Location
Suburban Washington DC
Originally Posted by jayjr1105
Isn't the best alternator a rebuilt one from a local alternator/starter service shop?
Those went away years ago with the advent of the internet and new Chinese models for $50. Nobody would pay the $150 to rebuild theirs.
 
Messages
1,760
Location
Cincinnati, USA
Originally Posted by atikovi
Originally Posted by jayjr1105
Isn't the best alternator a rebuilt one from a local alternator/starter service shop?
Those went away years ago with the advent of the internet and new Chinese models for $50. Nobody would pay the $150 to rebuild theirs.
No they didn't. There's at least one place local to me, or I could mail it to one of several places found via google search, or there are places online where you can get rebuild kits to DIY. For example: https://www.maniacelectricmotors.co...-11-soul-regulator-brushes-bearings.html
 
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35,859
Location
ME
With 300k on the brushes you're a statistical outlier. There's got to be some junkyard models with 130k.
 
Messages
125
Location
Dallas
Originally Posted by jayjr1105
Isn't the best alternator a rebuilt one from a local alternator/starter service shop? I hear they often replace components with parts that are higher quality than the originals. Maybe this isn't true for all shops.
As someone else pointed out, such shops are emphatically on the endangered species list. There's still a couple near me and I normally do take a core alternator in to be rebuilt to improved specs, but looking at the market I can see why they're losing business to new Chinese alternators.
 
Messages
125
Location
Dallas
Originally Posted by schuylkill
Driving home today and my battery light came on. I have an ultragauge and it showed 11.73 volts, held there pretty steady for about 15 mile ride home. The car starts up. Battery is about 2 years old I believe. Original alternator and voltage regulator, just passed 334K miles. Regulator is external on the alternator. How can I diagnose what is failing?
External, separate regulators haven't been a thing since the 80s, FYI - modern alternators have a replaceable regulator/rectifier on the back of the unit, but it's not considered an 'external.'
 
Messages
4,112
Location
WA
Originally Posted by eljefino
With 300k on the brushes you're a statistical outlier. There's got to be some junkyard models with 130k.
Exactly what I was thinking. And I'd bet it's used in several models/model years.
 
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