Is my alt causing this?

[JEMT8]

So i was at work, parked my vehicle and accidentally left the lights on. I came out about an hour and a half later and shut them off and started it up just to make sure. I have a new optima yellowtop so I wasn't worried.

The volt gauge in my vehicle usually rests on about 14v, but when I started it and let it run, it was on what I'm guessing to be the 12v line. I thought that my batter may have drained so I revved my engine to put some juice back into it and as i did, the needle kept moving up to 14v and back down to 12v with my RMPs. I drove it for about 10 minutes and it did it the whole time and when I parked it, it was still at the 12v line. So i just shut it off and went back into work since it started fine.

I came back out 4 hours later to go home and the needle on my gauge was back up to around the 14v line again like normal.

Anyone know what could be causing this or was it a weird phenomenon?

[finkster]

well the batt had enough to start it so its not dead. Sounds like maybe the alt took a shit while at idle charging the battery back up.

[JEMT8]

well the batt had enough to start it so its not dead. Sounds like maybe the alt took a shit while at idle charging the battery back up.

Could this be a sign that my alt is shitting out?

[hdorre]

Could this be a sign that my alt is shitting out?

He pretty much said yes

[JEMT8]

He pretty much said yes

Well I wasnt sure if he meant just a temporary shit. I'm asking if it means that most likely in there near future its going to be done for good sinnce it seems to be working now.

[audiofanaticz]

Could this be a sign that my alt is shitting out?

Its hard to say.

Charging a dead or heavily drained battery with an alternator can blow the alternator (even if it is an after market high output alt).

Your battery could of just been that drained it took a while for the alternator to charge the battery back up.

Easy way to test it is check your voltage at the front battery with a digital multimeter when the vehicle is off. It should rest around 11.9-12.9 volts.

Next go and start your car and check the voltage again at the battery. If the voltage is 1.5-2.5volt higher then the voltage you test when the car off chances are its charging normally.

If your still concerned you can take your vehicle/alternator to an autoparts store and have them do a test to see if its good (wont work totally right if you have a highoutput alternator). But the autoparts store guy will be able to load your alternator down to about 80-100amps and see if it is good or not.

Your best bet is to put your battery on a charger to reduce any risks of something going bad, and just monitor your voltages for a few days.

[MECHMAN]

Dude, your battery was just discharged from running the headlights, that's all. It takes time for an alternator to fill the battery back up, that's why your voltage was low when you started up the truck. All alternators make more current with higher RPM, when you revved the truck the alternator had enough output to instantaneously increase the resting voltage of the battery, when the rpms came down, it would fall back to it's low battery voltage. Once you drove around for a while, the alternator had the opportunity to bring the battery back up to normal. Don't worry about it, it's fine.

[Guest DC Power Kyle]

Dude, your battery was just discharged from running the headlights, that's all. It takes time for an alternator to fill the battery back up, that's why your voltage was low when you started up the truck. All alternators make more current with higher RPM, when you revved the truck the alternator had enough output to instantaneously increase the resting voltage of the battery, when the rpms came down, it would fall back to it's low battery voltage. Once you drove around for a while, the alternator had the opportunity to bring the battery back up to normal. Don't worry about it, it's fine.

This.