If the butterflies have remained open since you first installed it, it could be the way you have the vacuum line hooked up. Unless Kury has changed the instructions, they were wrong when I installed mine and mine was doing the same as yours. I called Kury, talked to one of the techs and he told me where to put the hose and what to block off...it has been working fine since.
Sorry, but, I can't describe exactly what was different. The Kury man can tell you.......it was an easy fix.
