Charging System/Alternator HELP!

Hi everyone,
I broke down yesterday; my tachometer went to 0, followed by my speedometer going to 0, then my truck sputtered and died. I pulled my alternator and battery (both fairly new (alt. is denso reman.)) and ubered to an autoparts store. They tested both, battery was mort (no surprise), but to my surprise they gave me a new one under warranty. Alternator was fine (this was a bench test on Autozone's machine). I made it back home and have been trying to figure out what is going on.
I followed some basic alternator tests and it doesn't seem to be kicking on. Upon starting the vehichle the voltage stays constant. I found this thread:
https://www.tacomaworld.com/threads/new-battery-and-alternator-still-not-charging-help.676487/
and started checking conductivity between the ends of the three wires. All showed a low resistance, but two were jumping between OL and that. Both were wore near the 3 pin connection. I ended up pulling the pins and soldering in some new wire on two of the wires. Put everything back together and plugged in the 3 pin connector to the truck while it was running (I forgot to plug it in) and I HEARD the alternator kick in for a couple seconds and I saw the V across the battery jump past 13. I thought I fixed it! But after a few seconds, I heard a change in sound from the alternator and the V went back down. I let the truck run, applied load to the battery, and it never kicked back on.

I disconnected the 3 pin connector from the alternator and checked V vs. negative terminal of the battery:
White: 12V all the time
Red: 12V w/ key on
Yellow: 12V w/ key on

I have no idea what else to do and I'm not sure if I will be able to drive to work tmrw. Debating going back to an auto parts store and having them test the alternator in the truck even though I feel as if its an issue with the charging system.

Any help is appreciated, explain everything to me like I'm an idiot please. Sorry for the essay, just trying to be thorough. Thanks!

 

Check all your ground straps including the ECU ground that I believe is bolted to the intake and negative ground that goes to the inner fender and engine ground to the body.

 

I will look at that too. I admitted kind of freaked out yesterday. Once I realized that the IG terminal was sending 12V to the alternator to turn it on but it wasn't turning on, my thought was that the alternator or at a minimum the voltage control module had to be the issue. Went to Autozone, bought a CarQuest Reman., stuck it in. No more charge light, and well over 13V when running. The alt. I had in there was a reman. Denso alt. from Rockauto, and it looked horrible when I got it. Now I have to get a new warranty alt. from rockauto, return the CarQuest one, then return the bad Denso one to RockAuto. I don't know if you have any experience with the re-manufactured Denso's, but the one I got looked like they packaged up someone's core and sent it out.
Problem seems to be fixed, but I plan on keeping a close eye on it. I think there were a couple problems including a failing alternator and bad wiring harness. I am also going to order:
https://www.rockauto.com/en/moreinfo.php?pk=13081413&cc=1429084&pt=2528&jsn=902
For a clear concise.
Thanks for the help.

 

Re-posting this from the other thread because it helped me a lot in the off chance someone else finds this thread.
http://wilbo666.pbworks.com/w/page/39441708/Toyota Alternators

 

So what is the voltage that that truck should be reading at idle? Mine is 13.5

 

Sorry for the super late response, mine reads the same at idle. I haven't had any problems since getting a new reman'd alternator, the one they sent me before was definitely someone else's core return.