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Discussion Starter · #1 ·
I am having charging issues on my 2004 Elantra. I have had the alternator checked at two different NAPA stores and have replaced the battery. I checked the voltage at the battery this morning with the car running and got a reading of 14.4 volts for about 30 seconds then the motor idle changed and the voltage dropped to 12.0 volts and does not change when I step on the gas to bring idle up to 2000rpm. Any suggestions out there??
 

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A lot of weird electrical problems are caused by poor connections of both the negative and positive battery cables. If it were my car, I'd physically, completely remove both battery cables and inspect, clean the connections and contact points, and reassemble.
 

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QUOTE (lowbagger @ Jul 11 2010, 02:27 PM) index.php?act=findpost&pid=340780
Thanks for the reply, I did clean the battery terminals when I replaced the battery.
Okay, but it's my guess you didn't check the other ends of the cables. Therein lies the problems. It's just a guess, but I see weird problems like this everyday. It's just a really good place to start when you start having inexplicable electrical problems with an older Hyundai.
 

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Inspect voltage at positive lug on alternator... see what the voltage is compared to what you have at the battery...

14V at alternator lug and 12 at battery post, major drop in the line from alternator to the junction block and then off to the battery... I have had a Sonata actually melt the plastic at the junction block post enough that the melted plastic got between the post and terminal and insulated it...

We do replace the random alternator on the Elantra, though not very often.
 

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Discussion Starter · #6 ·
I don't want to sound too dumb but by alternator lug you mean the B+ post on the alternator? I checked the voltage at the post first with the car off and came up with 12.3 volts at the alternator post and the battery pos. terminal. After starting the motor I got readings of 11.7 volts at both the alternator and the battery.
 

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QUOTE (lowbagger @ Jul 12 2010, 11:22 AM) index.php?act=findpost&pid=341005
I don't want to sound too dumb but by alternator lug you mean the B+ post on the alternator?
Yes

I checked the voltage at the post first with the car off and came up with 12.3 volts at the alternator post and the battery pos. terminal.

After starting the motor I got readings of 11.7 volts at both the alternator and the battery.
Not 14V at alternator... alternator is dead...
 

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Discussion Starter · #8 ·
That is what I have been suspecting all along. What I don't understand is how it is passing the bench test and failing in the car.
 

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You still have that plug-in connector there also... I would have to find diagram to see what drives the wires in the connector..

White wire is the main for the charging system

Red is hot all the time

Blue/Orange trace goes to charge lamp, fuse #2 in the pass compartment fuse block, pre-excitation resistor too.
 

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the 14.4v is being seen because normally without a voltage regulator the alternator will just keep on increasing the voltage in a runaway fashion,until the voltage regulator within the alternator electrically (sees) the voltage and then switches on to its predetermined regulated voltage 13.8v
In the couple of seconds it takes the voltage regulator to (see and regulate)the voltage the alternator can reach the 14.4v you are seeing on the meter, this happens automatically every time you start the engine.Because of the millions of voltage regulators made you cannot guarantee that they (All) show 13.8v so you have to appreciate that the regulated voltage could be between 13.4v to 14.2v neither of which would damage the battery whilst charging.
On a bench test the revolution of the alternator is usually fixed to a known slow speed that would be enough to show maximum voltage of the voltage regulator = approx 13.8v and not a run away voltage like when the engine in the car starts and is revved.
 

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Thread is a wee bit old.
 
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