i have a 2000 f350 i went into town yesterday morning to get oil and brakes and stuff to work on my dads 6.0 dually. i spent all day trying to get it started cuz its been 0 here for the last week and i think the block heater finally quit on it. well anyways back to my truck i left it run on the whole time i was in town brought it home parked it and got dads to run well i got home about ten last night and went to start it and it cranked really slowly. it finally started but it would only read it was charging 10v if i reved it up it would got to about 12v i have a manual voltage guage. i shut it and tried to start it again and it just clicked so i got the battary charger out and put it on it. i looked at my voltage guage before i put the charger on it and it was below 8 its hooked up were it works all the time. i put the charger on it and cant get it to do anything no lights no nothing the guage wont read off of 8v i tested the batt and they tested good. i cant figure out why it will not charge any at all not even enough to turn a dome light on and the batt were fine it didnt even show them to be low. my alternator went out about 3 months ago and i had it rebuilt did it go out again? and drain everthing? but it still makes no sense why even with the charger set on the highest engine start level it would not do anything. like i said its cold about 10 below right now i figured i would ask you guys since i can sit in the heat and do that lol. im going to try to pull it to a buddies shop and work on it 2maro. il try to replay later on tonight il prob be all day loading wheat. Thanks for anyones input Justin

 

Check all your connections. It sounds like a bad ground to me.

 

Could have toasted a battery(s) when the alternator went out. Take them out, charge them, then bring them in to be load tested at a parts store. And clean all the connections. Even if they already look clean do it again just to be sure.

 

Sounds like a loose connection to me.

Check all battery cables and power leads.

 

I'm in the check for loose leads group.
Done a lot of battery work lately and it amazing how much difference a loose connection makes.

 

Is it possible a bad diode in the alternator causing any charge to be drained off? We had a bad alternator in one of our trucks that would drain off at night...

 

i think its your alternator as well. might have gotten a bad part in there during your rebuild. i also just had an experience with my alternator grounding itself but that was after i tried to paint part of it using metallic paint.....

 

i figured out what was wrong with it last night. one of the battery were bad and it was sucking all the juice out of the other battery and the charger. i got it started after i cleaned all the connections again and the alternator seems to be charging fine.

 

Glad you got it figured out. How old were the batteries? They should always be replaced in pairs if they are older especially.

 

they were not very old maybe 6 months at the most.

 

Glad you got it worked out. I would think you should be alright replacing just one if they are that new and the other one wasn't damaged in the process.