'99 Ford F150 4.6... sooo, my battery light came on 2 days ago, was on pretty regular today on the way to work. Generally would come on during accelleration. As the day progressed, the truck became harder to start, so I had my wife look up the problem from her computer and she is saying a fuse could be the problem?? I am now out of gas on the side of the road with a dead battery, and even when I jump it it wont stay running!!! Is this a fuse, and if so - where?? Or is it just an alternator? I only have 70K on this truck... a little help please?

 

If the alt died and you did not fix it the batt will be drained and a jump wont work due to the alt not working.You need to charge the batt not jump it.Start the truck and check the voltage at the batt with it running.This will tell you if the alt is working or not.

 

Sounds like the alternator. When the light went on 2 days ago it was telling you that you were running off the battery. Now you have a dead battery and a bad alternator.

Just to be sure, check you charging system fuse in the fuse panel.

An easy road side check of a bad altenator is to start the engine by jumping it, removing the jump cables, remove the neg. side battery terminal, and if it dies the alternator is bad. Of course this only works if the battery isn't dead.

If you leave the jumper cables on for say 1/2 hour while not trying to jump start you should be able to charge back up partially your battery to check it.

Good luck........

EDIT: correct voltage with a meter is 13.8 to 14.8 volts while running .... anything else and its bad.

 

You have an alternator that has "bitten the dust".