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Discussion Starter #1
At idle and with the following loads on, I've noticed there's a significant system voltage drop (hovers around 12.9v/13v). As soon as it's off idle, we're back to 13.9. - 14.1v.

* Headlights (low beams)
* Rear defroster
* Blower fan on speed 2

That is not an unreasonable load and I know as long as I'm above 12.9v the battery is charging or at least getting maintained. But if I throw on seat heaters or another light, we're dropping even more (again, not unreasonable in winter).

I've already:
* Voltage drop tested between alternator and B+, B- to various parts of the body and engine (alternator)
* Cleaned grounds on body and wires to various parts of engine bay (B- to body, engine to body, ground point behind coolant expansion tank).
* Replaced battery last year. Have not had it tested because after shutting off and letting it sit overnight, it's still at 12.6v. Getting it tested is my next step.

Cleaning up grounds gave me back ~20mv in drop (yay?!) and the highest drop is 20mv between body and engine. Virtually no drop in any other location.

I know the alternator doesn't put out full amp at idle; does anyone know what the idle amp specs are for the Valeo 849101 which is the OEM alternator rated at 110amps once above idle.

Can someone with '11-'13 SFS check their reading with the loads above turned on?

So aside from getting the battery tested, getting the alternator bench tested maybe a poor ground for the defroster since I can hear it humming once on (anyone know where the ground point is in the back?)

Any other suggestions/tests or have had a similar issue (and got it resolved)?
 

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I don't see anything wrong here.
Just don't sit idling for extended periods with all the accessories on.
This is why police spec cars get heavy duty alternators.
 

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Sounds like nothing is wrong with me either. What you have observed is all pretty much what I have observed in the past with a little voltimeter that I can plug into my cigarette lighter. Keep in mind - Hyundai cars do have a smart alternator that varies the voltage between typically 3 set points, 12.7, 14, and 14.6 volts.

12.7 is your battery voltage, it should only drop below this when accelerating.
14, and 14.6 are where it will charge your battery and my car likes to run these voltages about 75% of the time. At a low steady idle my car even has trouble maintaining 14 volts with the headlights and A/C blowing. There is a warning in my user manual about leaving on too many accessories and continuously idling the car.

If you are just stopping at red lights, you won't have any issues (otherwise hyundai wouldn't have designed the system the way they did). If you are going to be idling excessively on a regular basis, just keep your lights off.

Good job cleaning up the grounds (a good idea for any hyundai owner), but don't spend anymore time or money on this. Let me know if you have more questions.
 

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Discussion Starter #4
Thanks for the replies so far. Only reason I even noticed this was on a hot day after about 30 mins of driving, I have the AC on, lights on and am seeing voltage dropping as I'm hitting the brake (again, adding more load with stop lights). I kick on the rear defroster and seat heaters for s&g and see it drop even further. I never really monitored it before so didn't know if it was a cause for concern. I think defroster itself takes a 40amp fuse (not that it's pulling all that at once) so with lights, cooling fan running from the AC and lights I'm probably over the comfortable idle output amperage. As soon as RPM's go up, so does the voltage (and available amp).
 

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Typically defrosters and seat heaters are turned on when a car is first started. When a car is first started in cold weather, it typically idles much higher, allowing the alternator to still charge the battery. So you're really stressing the alternator by running it with all of those accessories :-X Are you monitoring your voltage the same way I have?
 

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Alternator is charging when the ECU tells it to charge. Your car is working as designed. SBR can confirm as well.
 

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Discussion Starter #7
Typically defrosters and seat heaters are turned on when a car is first started. When a car is first started in cold weather, it typically idles much higher, allowing the alternator to still charge the battery. So you're really stressing the alternator by running it with all of those accessories :-X Are you monitoring your voltage the same way I have?
I have a Scangauge and have used DVOM to see the voltage at various loads. The alternator has nothing to stress about (bad joke...).

Thanks
 
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