I'm using a 110vac to 19vdc 2.1amp supply to power 3 hair dryer fans for a forge air supply. The issue is when I try to quickly increase or decrease the output through my lm317 voltage controller the fans begin to pulsate slowly instead of blowing. I can mitigate this by very slowly adjusting them, although this isn't a practical way to use it. Previously I didn't have this issue but I accidentally destroyed that controller and I don't believe over heating is an issue. What would cause this?