My 2001 F150 4.6 sits in the garage most of the time. The last two weeks or so it has been hard to start or seems to draw the battery down too much. The battery is a little over a year old and tested today at 97% charged. The alternator is charging at around 14.3 amps according to the tester from my local O'Reilly's. Today it was driven for a few hours, but after being parked for awhile, really struggled to start-dim lights etc. I cleaned up the terminals and cable ends, but it doesn't seem to help. What am I missing?

 

14.3 amps isn't nearly enough, or is that 14.3 Volts? Sounds like a bad alternator to me, if it will start to run badly. If the alternator worked, it would run indefinetely.

 

14.3 volts

 

You might have a lot of corrision inside the battery cables. A test on the postive cable is in order. If that checks out I would look at the starter.

 

14.3 volts while running is about normal. If you have a battery load tester try it with truck off and then again about an hour later. It should be holding at a minimum of 12 volts.

Sounds like a bad battery to me. Just because its a year old does not mean anything. I have had them go bad on me after 6 months and thats why I do not buy interstates anymore. Our work trucks would eat Interstates also. I am not sure why but NAPA batteries last much longer in our trucks and I think they are made by the same company. I never had much luck with Autozone batts either.