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C. Walker, Jr.
C. Walker, Jr., Auto Mechanic
Category: Hyundai
Satisfied Customers: 710
Experience:  Shop training and experience.
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2010 Hyundai Sonata alternator showing 30 volts AC

Customer Question

2010 Hyundai Sonata alternator showing 30 volts AC
Submitted: 6 months ago.
Category: Hyundai
Expert:  C. Walker, Jr. replied 6 months ago.

30 volts is very high. This normally means the voltage regulator is bad causing the issue. What kinds symptoms are you having?

Customer: replied 6 months ago.
Battery goes dead after sitting 8 hours. When I started parasitic voltage test this AM with everything turned off there was a voltage draw of 11.95 volts. I pulled all fuses one at a time and voltage never changes. When car is running DVM shows 14.4 volts. Battery is new. When I switch to AC volts it shows 30
Expert:  C. Walker, Jr. replied 6 months ago.

How are you performing the parasitic draw test?

Customer: replied 6 months ago.
disconnected neg battery terminal connected one lead of DVM to neg terminal and other lead to neg cable. Set DVM to DC 20 volts
Expert:  C. Walker, Jr. replied 6 months ago.

Lets try doing the test but with the positive terminal instead. Make sure that the positive does not touch the battery at all only the leads of the dvom

Customer: replied 6 months ago.
Did you get my last message??
Expert:  C. Walker, Jr. replied 6 months ago.

yes I want you to try the parasitic draw test using the positive terminal instead of the negative terminal.

Expert:  C. Walker, Jr. replied 6 months ago.

If it comes up with the same reading we will need to start disconnecting all major components including the alternator starter and the fuse block where the power wire comes into it. This would be a MAJOR SHORT!

Customer: replied 6 months ago.
Sorry about the delay. Minor family emergency (Toilet) Let me run the test off the positive terminal and see what I get. Since alternator was showing 30 volts AC. I was thinking bad diodes, I guess quickest test would to disconnect alternator cable but it's a real pain in the butt to get to.
Expert:  C. Walker, Jr. replied 6 months ago.

I like to make sure before replacing the parts it is better than just swapping stuff off. Once we make for sure than we replace.