I had an old Thunderbird I bought as a kid, every morning after I bought it I went to start it up for work but it was dead. I was a kid, no money to fix it, no skills on figuring out what was wrong or how to fix it. I got a new bettery thinkin it was OK. Next day i was late for work. Checked alternator, solenoid. Copuld not figure the thing out. One day I had to disconnect the power seat for something, problem went away. For a few weeks now when I have gone to start the van, it seemed like it was low on juice. I have 3 AGM bateries, 2 of them huge 100aH. It's been on my mind, but was always hard to tell for sure if there was an issue. Today i went to bring Brandy to work and it wouldnt start. Was all bt dead, would almost turn over, then click clikc click. I kept trying and trying, got it to start. Of course charging 3 giant batteries... most likely killed the $400 HO alt, it's running right now and volatage is below 14V
Hre is what i would do... Pull the batteries, charge each one up fully and then have them load tested. Individually.... Could be one bad battery taking down the other good ones.. And also double check your alternator, it may be fine. Put in a known good battery and see what kind of voltage you get
