92 F250 IDI 7.3. Here's the problem and I can't figure it out, and nowhere have I seen this specific problem. First of all keep in mind both batteries bought beginning of this year. Amp light came on bout a week ago, so I ordered an alternator. I work in the oilfield so it was going to have to wait until I had an available day well Monday I was getting ready to leave work and go home and install, and my batteries had a very low charge and my turnover was less than great. So I hurried home and by the time I got there the batteries were at normal charge. I kill the engine and get to work takes about 30 minutes and I swap alternators. I get back in the truck and check to see if my amp light has gone away. It has, YAY!!! But the batteries are still way to low to crank. I had just enough power to get her going again. So I check all the connections and look again and they still are low. I plug in a trickle charger and wait till yesterday morning she's fine before work. But I need jumped before I can leave last night. Now this is were it gets interesting and help is needed: I get home and batteries a completely normal charge on the dash. I kill the truck and immediately turn the key back on. Within a matter of 2 seconds the batteries have completely drained out to below 8 on my gauge. What gives?? I understand overnight and over a period of time batteries losing some charge but to go from full charged to barely starting the truck right after I turn it off?!?!?! What do I do?? Thanks boys. BTW New to the site been reading here for months thought I'd join.

 

I would take the batteries to an auto part & have them checked