I have a 1997 F150, only 48000 miles, had no problems till yesterday when i went to go to a fire call (fire dept) and the battery was dead. Jump started it and went about the call and things. Left sit overnight, and the next morning it was dead again, no lights were left on and the alternator is putting out 13.8. Something must be draining the battery but what???? Anyone seen this problem before, maybe a bad ground somewhere or ??? Any info would be much appreciated....Thanks Tony

 

I assume it's the original battery?

If so, have that tested. Make sure the fluids are good, it's holding a charge, and it's healthy enough to still be used effectively.

 

If it's the original battery, it's time for a new one. I had to put one in my 97 Merc with only 30K miles last year.

 

Go get the battery charged and load tested.

 

A shorted rectifier in the alternator stack will do this and still charge enough to run the motor after a jump start and even charge the battery.
A shorted cell in an old battery will act much the same.
6 cell battery is 2.17 volts each for a total of 13.02. One cell missing and you have a problem.
A possible hint of a bad alternator is to feel the case for being warm to the touch after the motor has cooled indicating the alternator is causing a draw out of the battery due to it's defect.
Otherwise a system test will generally find the problem.
A special LED voltmeter for this purpose will indicate problems with the whole system if you watch the actions of the LED at starting and during re-charge running.
It's all in interpeting the action of the lamps as directed by the instructions.

 

Thanks for the help guys, turns out it was a combo of both the alternator and the battery, i figured the battery was going bad and it took the alternator out with it. I will also share that after taking off the alternator i found that it was a NAPA brand with a lifetime warranty so i got a free alternator and bought a new battery and now back in business!!