Battery/Alternator Help

[mah77]

I replaced both batteries just over a year ago. Ive noticed the battery warning light on my dash has been turning on and off intermittently for the past few weeks. This morning I went out to start it up, and gave that annoying rapid clicking sound and dash lights went out. I tested 11v at each battery. Turned the key to "on", and each battery dropped to 8v. As all the accessories began their pre-start, each battery dropped to 7, 6, 5, and eventually 0v. I'm not looking forward to pulling both batteries and taking them to the autoparts store for testing, if I don't have to. I'm curious whether it's a battery issue, or possibly an alternator. Any advice?

[Harley Strokin']

I had the same problem with the dash light coming on and it ended up being the alternator and one of my batteries had a dead cell, so 2 new batteries and 1 alternator later I was good to go. Definetely get the batteries tested so you know your system is producing full power so you dont kill your FICM.

[mah77]

Thanks Harley!

I pulled the alternator and took it to Napa. They tested it 3 times at 13.7v, 13.9v, and 14.1v (Passed) I asked them to test the replacement I was going to get, and it tested at 7.9v, 8.6v, and 9.3v (Failed). I thought that was strange, but took the plunge and swapped them out. I jumped my batteries off my other vehicle, and started the truck up. Took it for a good 30min drive. My battery light never came on, and after 4 start and stops, it cranked just fine. I guess Napa's machine wasn't working, cuz the truck has been fine all day. Only odd thing is I found 2 blown fuses (fog lamps and the trailer battery charger).

[Harley Strokin']

Yea I seem to remember my trailer fuse blowing too, maybe their tied in together somehow? Idk but I'm glad it worked out, that little battery light can really get annoying.