I have pulled up 6 alternator threads which I am going to read through today, BUT, quick question. When I bought my LX in July the truck would start up just fine. But after a few days/weeks I noticed it was having a harder time turning over although it always started. I was not noticing dimed lights, but mostly using truck during the day. I replaced the battery with a 27f interstate from costco.
I have been trickle charging randomly over the past month just because I bought a 4amp battery tender and want to keep it topped off. When I measured the voltage on day 1(just a couple of days ago but calling it day 1 for simplicity) it was 12.34 volts. The next day it was ~12.27 volts-I may have drove it around I can't recall. I trickle charged it again overnight after measuring 12.27 volts and its back up to 12.34 volts. This is a brand new less than 1 mo old battery. I then checked voltage again today(day 3) after crusing around at low rpms/non freeway for ~20 minutes and it was 12.34 volts. While the truck was running it is about 13.3 volts. If I rev to 2500 rpms the voltage does not change(at least not significantly, it appears to fluctuate a bit but seems to do this when engine is not running as well).
I am thinking simply my alternator is going bad or barely functioning? What number should I expect to see if I plugged the battery tender in for say a week? It doesn't seem it will go above 12.34 volts-could it be a bad battery? I'll plug battery tender in again overnight and see what number I get tomorrow morning prior to driving it.