Hello. I drive a 2000 F-150 4 x 4, V-6, EFI, A/C, ABS. Yesterday while driving on the interstate w/ my headlights on, my dash gauges and radio quit. When I turned off the lights, they all returned immediately except the alternator which was flat. Then, w/o any changes, it sprang into service, charged the battery enough in abt 15 miles for a restart 30 minutes later, but almost immediately upon returning home, it charged for a few minutes then slowly went flat (0) again. By the time I'd traveled abt 20 miles, the truck died but was easily jump started and fortunately I made it home but the battery is too dead now to turn over the starter. It seems that once I get the engine started. the alternator works until the battery is charged then shuts itself off or it may only work for a specific period of time. FTR, the battery is new and under warranty, the alternator is the original. My question: is this a simple alternator problem or could there be more complex (computer, fuses, etc problems or both or ?? And can I diagnose these w/o an expensive machine?

 

About the only thing you could check is the voltage at the alternator B+ stud. This will ensure there is no short or open circuit in the b+ wiring between the alternator and battery. Beyond that you've done more than most folks and if the above doesn't show anything, time to replace the alternator. A 13 year old unit did fairly well. Don't let it go too long or it may end up killing your new battery if not already limiting it's peak capacity.

 

Thanks, Stormsearch.