Car is a 2008 Hyundai Tucson with 2.7L V6. Neighbor’s son use it to go to new job interview. He drove it to his place after. Next morning battery was dead. His mother drives to his place to be there for a AAA jump. She said it took the heavy cable plugged into the back of the AAA truck to start it, …

[image] Fresno-Jack: I never have a problem with a weak battery. You never had an issue with the light bulb until one day you hit the switch and it stopped working… lol Things can go bad without any warning, it happens… Cleaning the battery and cables may have been all it needed, or maybe t…

[image] Fresno-Jack: Battery was at 12.3 volts and the car started right up. A good battery should not end up at 12.3V after sitting overnight, even tho’ that will likely start the car. Apologies if I missed the part where the battery was load tested - maybe when the alternator was tested? Bu…

[image] cigroller: A good battery should not end up at 12.3V after sitting overnight, even tho’ that will likely start the car. This reading was taken after the battery was completely discharged, the engine jump started, and the car driven for 1.5 miles. After charging, and surface charge dis…

Something doesn’t seem right about the situation. Battery is dead enough to need the “big wires” jump and yet, after only a couple miles drive, appears to be reasonably charged? Jump goes from chassis to positive terminal. Battery is out of the picture. Perhaps a bad connection from the positive cab…

[image] TwinTurbo: Perhaps a bad connection from the positive cable to the positive clamp…or ground wire, engine to chassis? This is the only thing that makes sense to me too. As I noted in the original post, I cleaned the battery posts and cable clamps before charging. I did not go so far as…

[image] Fresno-Jack: The only thing that does not seem to fit with a generator that tests well is that the voltage at idle under full electrical load drops to 13.05 volts. If that was before you recharged the battery, the battery may have been drawing 40 amps from the charging system. That wo…

Alternators come with different amp ratings. The amp rating is at a specified RPM, it will be lower at low RPM and higher at higher RPM, but for comparison purposes, an alternator rated at a lower amperage will be lower at all RPMs that an alternator rated at higher amperage. Alternators range fro…

Alternator output voltage at idle with full electrical load

Maintenance/Repairs

Fresno-Jack July 16, 2025, 1:39pm 5

Yesterday the owner took the car to AutoZone this time to get the alternator checked. She said the guy checked it 4 different ways (?), and each time it show the alternator was good. So everyone has, as you put it, moved on.
Thanks

Topic		Replies	Views
Alternator The Show	6	1262	August 29, 2011
Alternator & Battery Light Maintenance/Repairs alternators	4	2002	July 30, 2011
1989 Chevrolet Van - Alternator Maintenance/Repairs chevrolet	2	254	March 25, 2019
Good battery/altenator but no charge? Maintenance/Repairs hyundai , sonata , batteries , volt	5	872	January 9, 2011
Battery not being charged, how can I be sure it's the alternator? Maintenance/Repairs subaru , legacy	5	938	June 13, 2022

Alternator output voltage at idle with full electrical load

Related topics