i have an issue with my 2005 f150... the battery light came on today and when i revved the motor it would go off.. i tried to make it to auto zone to have the battery checked but a couples miles from there the truck shut off.. the battery would take jump but after a few minutes of running the battery was depleted again... i finally managed to get it home and let it run to charge the battery back up but when i tried to turn the lights on while it was running in park the lights wouldnt turn on and when i shut it off the lights came on and wouldnt go off til the battery died.. Any suggestions or guidance?? could this just be a bad battery. i replaced the alternator two years ago but the battery is about 5 years old and the battery cells were dry. put water in them to get it home.. please help........

 

Batteries generally do not just stop working while you are driving. As long as the truck is running, it should stay running if your alternator is working correctly. if you got your alternator from auto zone, i would suggest getting it tested, as it will be under warranty. sounds to me like you must have some sort of parasitic draw, possibly in your alternator's voltage regulator. however, the lights have me confused a bit. could be drawing in the lights maybe? but that's where i would start. Keep in mind, a bad alternator can damage a good battery, do to over and under charging.

 

Batt over five years old? Dry cells, needing water?

Pitch it, not worth messing with, period. Clean up ground points and connections at block, firewall and frame, check alternator connections and grounding to block. This is important.

Dried out battery may not be "the" problem, may only be a symptom. Use your voltmeter to check for 14.X volts at high idle, with lights and heater on after new battery is installed. Always charge up a new battery before installation, no matter what the kid (or old guy) behind the counter says. Bad battery can roast alternator and the reverse is also true.

 

I'd have to agree with Ted. No matter what you replace first, don't run it long without checking to make sure everything is working properly. For example, to test your alternator, and get accurate readings, you must have a good battery. (if you have autozone test it) if you replace the battery double check to make sure everything is producing and maintaining proper voltages before driving it. same goes for the alternator.