SR Alternator- 4 volt output

[KeiStarr]

I recently did my sr swap, everything is working great except the alternator power output. I started to drive the car after the swap and noticed the power was spiking. Once I got back to the garage I went to check the alternator and it was pushing out only 4-5 volts of power. My first guess was maybe the alternator was going bad so I took it out and got it check along with the battery, both passed testing. I swapped the alternator with another just for good measure, and used another lower harness (both off of a good running car). I'm pretty sure everything is grounded as well.
Any suggestions to my situation? Thank you in advance.