Battery or Alternator issue??

[Calico_NC]

Okay so recently my car has been dying from playing my radio for about 10-15 minutes without the car started..All of a sudden now, it doesn't want to stay started unless I hold the gas pedal down. I did test #9 on my OBC and with the key at position 2 (not started) it measured 11.90volts and it would somewhat decreased the longer i left it at this position. When I turn the ignition on, the reading jumps from 14...to 13...to 12..to a sputter and suddenly off, unless I hold the gas pedal down in which the voltage cranks up to 14. My question is, do you think this is a sign of a bad alternator or battery, or even bad spark plugs.

Also, just a little more back story..that same day before this problem occurred, i was driving home from a 200-250 mile trip and the car ran hot a couple times (ugh a whole other story). The coolant temp came on a couple times, but it ended up stabling out. Could this also have caused this problem?? Could the heat possibly fried the alternator or something along those lines?

Another fact...I probably purchased my battery around 2006..just factoring in that little bit of info.

[Ross]

You may simply have a loose fan belt not turning the alternator or water pump consistantly. With the two symptoms you mention I'd start there.

[BennyM]

Second on the belt.

[Tiger]

Dead battery. Battery needs to be 12.7V for full charge. At 11.9V. it is less than 10% capacity.

If your voltage at 2000RPM is 14V, alternator is good. You can do a load test on your alternator to make sure it is running at spec. Autozone does free test.

Autozone is good battery at awesome price. Latest batteries I got from them is still working great... after 4 years.