My battery measures 10.15V cold, and then 10.57 with the engine running. Is there something wrong with my alternator? The alternator's job is to charge and keep the battery running at a constant voltage when my engine is on right? Well, my battery's voltage starts fluctuating when I rev the engine and play my system, anywhere between 10.1 ~ 12.6V. It's not even hitting 13.8 or 14.4V I'm not sure what's wrong .. any ideas before I give this to the dealership on Monday would be appreciated.

 

It sounds like you have one or two bad cells in the battery. Have you checked the water level recently? What is the voltage at the alternator with the engine running?

 

How do I check the voltage at the alternator? At the shop, they say to just turn on the engine and retest the battery voltage to give you the alternator's voltage, but I was wondering what if there's something wrong somewhere in between the alternator and the battery terminal.

 

take to autozone and let them test for free, there machine tell how many amps alternator is pushing out too

 

There is a 120 amp fuse in teh main fuse block under the hood. I can't remember if it is between the alt and the rest of the car's electrical system or between the battery and the rest of the electrical system. The voltage level you have is about right for one bad cell in the battery. Or a battery that is toasted.It is normal for the alternator voltage level to drop at the battery terminal when the battery is chargeing. With the low voltage level of your battery it may cause the alternator to burn up fairly quick. I'm not sure.

 

i think you can measure it at the battery with the car running. for me, i get about 12.1 volts with engine off, and 13.8-14.1 with engine running. it should be in the 14s with engine running with a good alternator.

 

That is with a good battery. Remember the battery in question is 2 volts low. If the alternator is bad the battery may be replaced. The battery being bad could also kill the alt. It should have been tested the same day this problem was realized. Unless the owner has a second car.

 

Each cell of a battery is supposed to read 2.11 Volts. if you are readind around 10 volts the morning after, tou have a bad battery. When you have a bad cell it will sometimes suck the Voltage reading down while running. Start the car, and disconnect the ground of the battery. If the car is still running the alternator is probably fine. If the car stalls, you need battery, and alternator.