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Well I tested everything yesterday. Everything is checking good, its putting out 14.4 volts while running. both batteriess checked good, no dead cells.
what should I do next? I don't have access to a repair manual, can anyone tell me what fuses are in the system?
what are your batteries at without the engine running? 14.4 running means your alternator is putting out (no pun intended). i just dont trust the bench tester any of the auto parts stores have. a battery charger/amp meter will tell you all you need to know about a battery.
wow, that is good. I have never had batteries show more than 13.5
have you had the alternator load tested? here is an old school way of checkin it- start it up and take a wrench and touch to the back of the alternator. it should have a pretty good magnetic field. diodes are usually the first thing to go out. the last problem i had with the bat light coming on was only at highway speeds. it bech tested good and both batteries were good. a new alternator solved the problem. if you have done that though, it has to be somthing in the wiring.
I've a 99 F250 PSD and had that same issue this past summer. At an idle the light would come on and flicker then go out when the engine RPM's increased. Batteries checked out fine and belt tension was ok. I removed the alternator took it to to be tested and it failed testing. I installed a rebuilt unit ($135.00 and 12 month warranty)and the light has been off since.
Most likely the regulator which is internal is failing and the light flickering is letting you know of its inpending doom.