T-Slot &/or 20/20 Rocker Switch Box

(Long - the full story) (Scroll down to skip all the yada yada)

My FLSUN PRUSA i3 Clone instructed me to wire my extruder heat sink fan from the "constant on" 12v power supply on the Makerbase board it came with. Meaning, as soon as I powered on the printer, the extruder fan was on as well...All.The.Time... printing or not. It was a smart idea at the time for me as I was just getting started with 3D printing and had no idea what I was doing and how big of a role that fan plays in the printin