I have a 2006 f-350 diesel with a new set of batteries and another rebuilt alternator . After about 10 min battery light comes on and occationally goes off but then back on. Ran fine for weeks but now need to put on a charger every few days.

 

Welcome to FTE, kingraiderfan.

Sounds like you still have a bad alternator.

I have seen alternators that fail once they get warm. They act just like what you are seeing.

 

what u getting at the batteries and at the alternator?

 

rebuilt alternators sometimes are bad out of the box, I would take it back and get another.

Depending on where you bought it, they should be able to load test it on the truck.

 

get this fixed quick.low voltage to the ficm will kill it and maybe some injectors to.

 

Yep,,,started getting chilly in the am,,,my 06' Six-O,,started slower and slower ,,,load tested my Batterys,,,one was done,,other was still Good,,,Last year I replaced one,,,,this year I did Both,,,$210 for 2 CarQuest 1080 CCR at 32F,,,the truck never cranked over so fast as it does now!

With my Edge Insight,,I can look at the voltage,,,while running the old Bats where at 13.67 volts,,,alt is good,,,,with truck off,,,key on,,,volts where at 11.6,,and the morning I changed them,,,cold,, key on,,engine off,, volts at 10.6,,, Now,,with new Bats,,,running voltage at 14.02,,,, truck runs Great !

 

Well after going to the guy who rebuilt my alternator and finding out it was junk out of the box he rebuilt it with a differant regulator and were back in business. Thank you guys for saving me more money on blood pressure medication.