So I have a 1998 Ford Explorer that has 102,000 miles on it.
I haven't had any problems with it other than replacing the battery about a year ago.

But just a week ago, I went out to my truck and it didn't start. Me not knowing a thing about cars (I'm a girl) I just wiggled around the battery cables hoping it was some loose connection or something...Well it seemed to work because my truck started and continued to work for the next few days.

Today, it stopped working though. It just wouldn't start. It didn't even click or anything when I turned the key as if it were trying to start.

My friend whom works on cars has a machine that he brought over and it said that my battery was at 12.9 volts. He tried charging it because the machine said that my battery charge was at 0%. So we charged it to around 80% according to the machine, but my truck still wouldn't start. He didn't know how to check the alternator, so he wasn't sure the status on that...

He then wiggled my battery cables around again, and surprisingly my truck started.

Does anyone have a clue what might be wrong? He's not sure if it's bad connections or my alternator. Because before, I wasn't having any weird things happen like lights dimming out. Literally it was just dead one day.

Thanks for any help!!