I can put in a fully charged battery, start and drive around just fine, but if I let it sit for 24 hours there is barely enough juice to crank the motor.
Does this sound like the alternator? All four of the batteries I have been using checked out ok at autozone.
If you have freshly charged, good batteries and you run around all day long and toward the end of the day, your batteries are dead/weak, youve got an alternator problem....
What does your voltage gauge on your cluster say while engine is running? Mine is typically by the A of "NORMAL".
Even though the batteries tested just fine on a normal car battery tester, doesnt mean that they'll turn over a diesel engine just fine....
If you have charged batteries and let the truck sit for a day or 2 then the batteries are dead, your batteries are junk or you have an electrical draw somewhere. Time to start troubleshooting your electrical system at that point.
Try this......charge up your batteries and completely disconnect them and let them sit for several days. Reconnect ONLY ONE BATTERY and try to start truck. If dead or really weak, you've got a battery problem. If it fires up, disconnect that battery and try starting off ONLY the other battery. If it fires up OK, your batteries are fine. Keep in mind that both batteries are always connected and if one is junk, it will pull the charge out of the other one as well when they are connected.
If the batteries are similar vintage and you find one to be the culprit, change em both to avoid frustration in the future...
1993 F350 Crew Cab 4x4 4:10 gears, ATS turbo, E4OD,
SOLD - 1992 F250 Extended Cab, 4x4, 5spd, Naturally Aspirated IDI, 190,000 Miles, New trans, new clutch, new brake booster, new/used Stirling 10.25" 4.11 limited slip rear end, plenty more new parts to come soon.