99 tacoma 2.4 alternator and battery charging issue

So I looked through the threads here. I found a few answers but nothing fixed my issue. Maybe you guys can help.

So, I traded for the 99 tacoma I have now. It has the 2.4. I noticed the battery light would come on intermittently didn't have any issues though. I adjusted the alternator out to tighten the belt a bit and that night the alternator died.

I bought a new alternator and battery and installed them. (The check engine light had been on before the alternator install and went off after) but I'm still getting the battery light on as soon as it's started now.

I've checked voltage with my multimeter as I can't think of anything else to check. Voltage at the battery without the truck running is 12.40, after start up it goes down to 12.10 or even lower if I turn on any accessories. I don't have any idea what it could be so any help is much appreciated.