I'm having this recurring issue with my charging system. Voltage drops low while at idle. The alternator was just replaced by the dealer and it's still doing the same thing. Initially when I first found this problem, I heard the blower for the HVAC system slow down quite a bit, then I noticed the reading light was almost flickering. I checked the voltage at the battery terminals with the car at normal idle (warmed up), A/C on, and lights on, and the voltage was in the 12's. For arguments sake, I then turned on the rear window defroster, and the voltage dropped in the 11s.

Can anybody lend a hand and check their for comparison's sake? Just make sure the car is warmed up all the way so the idle is down to the normal RPMs, which is ~750. Turn your A/C on high, and lights on, then read the battery terminal voltage for me. The dealer claims that is normal.

 

You should be getting approx 14.1V (± 0.3V) at the battery when the engine is running. If you aren't, either the battery or alternator is bad or the wiring/connections are.

 

With the engine idling:

Measure the voltage between the alternator output stud and the battery + terminal - should be close to 0V.

Measure the voltage between the battery - terminal and bare metal in the engine bay that is attached to the body but away from where the battery GND cable touches the body - should be close to 0V.

Measure the voltage between the engine and bare metal in the engine bay - again should be close to 0V.

Like the first responder said, you are likely looking at a defective battery or a connection problem.

I do not agree with the dealer saying it is normal for the voltage at the battery to drop so low you hear a significant drop in fan speed or lights flicker. I can see maybe a 200mV or 300 mV drop.

Keep us informed.

None

 

I also have this problem on a new 2013 Sonata GLS. At idle and under any load, but especially A/C headlights and rear degogger, the battery will discharge. Dealership (Pohanka) informed Hyundai HQ that this is apparently normal, as the other 2013 Sonatas did the same thing.

Check youtube

2013 Sonata problem with electrical system

Please...if you know anything about this, please post an answer. Not what we all know, that batteries should never discharge at idle, but specifiaclly as it relates to Hyundai vehicles. I was actually told by HQ rep, that I shouldn't run car at idle with loads on!