ok so about i month or so ago i replaced my alternator then a couple weeks ago my #8 injector went out now my battery light keeps coming on and the one day it just was completely dead when it sat overnight so i charged batteries drove bout 15 minutes to work then right b4 i pulled in parking lot battery light came on again my radio went off and my heat started blowing really weak so i parked it turned it off then tried to restart it and it was completely dead, so i jumped it took it to napa they tested the batteries said good batteries but low charge, so i thought my new alternator was bad so i went to advance auto(bcuz napa didnt have machine to test alternator) tested alternator said it tested good aswell. Im kinda confused on my next step o and advance also checked to see if there was a constant pull on the battery and said it looked normal aswell which even with a constant pull i dont think it would kill it while im driving, but im no expert so thats just a guess. I just cant seem to keep this truck on the road right now

05 F250 6.0l 157500 miles egr delete 3in lift 35s sct tuner from innovative diesel

 

Go over your ground connections really well, sounds like even though the alternator is working itself, it's just not getting the power to the batteries.

 

Just because the alt tested good doesn't mean its good. My light kept coming on and volt dropping. Batteries tested good alt tested good. Batteries would drain after 2 days of not starting. Went back to the shop tapped the alt with a hammer and you could hear the alt. Turns out it was a bad diode and the light would come on when I hit bumps in the road. Replaced it with a HO no problems.

 

yeah mine will come on when just at a cruising speed then when i see it i hit the pedal a little bit and it kicks back off i just paid $220 for that alternator and they said its testing good so wont replace it what should i do. I was also told maybe one of the pullys are going out i can hear a slight squeek but cant tell which its coming from would that cause the problem or would that have nothing to do with it? i checked all my grounds and cleaned all the conections everything looked good.

 

You have a brand new alt already? Just give it a tap with a ball peen hammer and see if you hear it kick in and rpms raise.

 

Now that I think about this more, I had a buddy from another forum who went through almost the same issue... dead alt, dying batteries etc etc... replaced everything, still had charging and drivability issues. Replaced alt again, same issues... The thing that finally fixed it? He took the batteries off the truck and put them on a slow charge and charged both up to full capacity, put them back on the truck and his problems disappeared. I never really understood it, but all of his issues just went away after that. These trucks do some really funny things with low voltages.

 

Well the alt isn't supposed to charge dead batteries. Only to keep a fully charged battery fully charged.

 

the day before i posted my problem i took my alternator completely out of truck and had it tested it tested fine again so i put it all back together i charged my batteries and since then it hasnt had the problem except yesterday morning it had a weak cold start but thats prolly just because i forgot to plug it in and it got down in the 20s that night good old ohio . one of my pullies still has a squeek to it but i dont know how difficult it is to change them pullies plus my garage isnt big enough to pull into so i guess i will only fix it if necassary what do yall think?

 

I'm talking like a .5 volt difference... The truck was running and starting just fine, but having drivability issues. I would think it was close enough for the alt to keep it going, but who knows. I'm pretty open about not being an electrical guru haha

 

haha im no electrician just going off my own experience. Electricity is some tricky stuff.