How do you know if alternator is bad on a 2006 hyndai sonata v6

what i would do first is have my alternator check out, if bad will make all lights go crazy.

Did you check to see if the serpentine belt is tight or missing? The battery light comes on to tell ou there is a problem with the charging system. It does not come on when the battery is bad. Since the alternator and the power steeringpu p are run Blythe same belt it would make sense to check the belt to make sure it is there and tight and capable of turning these accessories.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Check the altinator for output volts and battery problems.

sounds like a serpintine belt issue what kind of condition is the belt in?

How is the alternator belt? There might be a loose connection at the battery, alternator, ground cable. Without a lot of detail, there are 1 way diodes in alternators, when the diodes go bad, the current will go the way it's not to, when this happens, it powers the light in the dash. Try wiggling the connectors, maybe that would make the light come on, if there is a bad connection.

Ok, the high pitch sound is your idle pulley bearings going bad. The splash of water is exactly that, the belt gets wet and slips. Definitely a pully, more than likely the idler pully.

Removal

1. Remove or disconnect the following:
   
   Negative battery cable Radiator mounting bolts, 1.6L only Alternator drive belt Alternator wiring harness connectors Alternator. It may be necessary to raise the radiator

Fig. Exploded view of the alternator-XG 300 and XG 350


Removal & Installation

1. Remove or disconnect the following:
   Negative battery cable Alternator drive belt Alternator wiring harness connectors Alternator. It may be necessary to raise the radiator
   


Fig. Exploded view of the alternator-XG 300 and XG 350

1. Before servicing the vehicle, refer to the Precautions section.
2. Remove or disconnect the following:
   
   Negative battery cable Radiator mounting bolts, 1.6L only Alternator drive belt Alternator wiring harness connectors Alternator. It may be necessary to raise the radiator
   
   
   
   Fig. Exploded view of the alternator-XG 300
   
   
   
   Fig. Exploded view of the alternator-XG 350
   
   
3. Install or connect the following:
   
   Alternator and reposition the radiator, if raised Alternator wiring harness connectors Alternator drive belt
   
4. Adjust the alternator belt and torque the bolts to the following specifications:
   1. Accent: Pivot bolt to 14-18 ft. lbs. (19-25 Nm) and adjustment bolt to 14-20 ft. lbs. (19-28 Nm).
   2. 2.0L and 2.5L Sonata, Elantra and Tiburon: Pivot bolt to 14-18 ft. lbs. (19-25 Nm) and adjustment bolt to 105-132 inch lbs. (12-15 Nm).
   3. 2.4L Sonata: Pivot bolt to 26-41 ft. lbs. (34-54 Nm) and the adjustment bolt to 14-18 ft. lbs. (19-25 Nm).
   4. 3.0L Sonata and XG 300: Pivot bolt to 14-18 ft. lbs. (19-25 Nm) and adjustment bolt to 11-16 ft. lbs. (15-22 Nm).
5. Install the radiator mounting bolts, if removed.
6. Connect the negative battery cable.

I hope hrlp you with this. Good luck and remember rated this help-

I would agree that it's the alternator. However, before you SPEND money, VERIFY that it's the alternator. Take/tow the vehicle into a Hyundai Service Center (dealership), pay the diagnostic fee. They will tell you EXACTLY what the problem is and what's needed to fix it (parts, labor, tax, time-frame, etc.). Afterward, you can fix it yourself.

autozone can tell you what is wrong but only if the light is on, they can check your alternator,battery and even your starter for no charge.