OK, I have figured it out. My Mains power fluctuated between 117.3-120.6v throughout the day. I'm on a community grid system, so the more power demand during the day, the lover the voltage. Just enough to cause a little flow variation in my return pump. Now, anyone know of a good power conditioner? I am going to try my UPS, see if its constant, but I think it fluctuates with Mains as well, only switches to battery on power fail....
Need to figure out how to make a auto Buck/Boost transformer
Edit, Nope, My UPS drops from 118 to 108 upon power fail. so it does not actively condition the power
