For Gits and Shiggles I tested it again with the same results. With my monovalve disconnected, no heat blew out the vents. With it connected vents blew very hot. The monovalve insert is brand new as of yesterday and the engine was running. I did not check to see if my a/c would work with the monovalve disconnected, but the heat sure didn't. The transition from hot to ambient air was not instantaneous, but certainly did not take minutes. The transition back to hot when I reconnected the monovalve was very fast. I could not believe that I was taking the time to check it again as I was quite certain of the previous results and quite frankly could not care less which way the monvalve opens and closes, as currently my climate control system is working as it should and that's what I care about.

Andrew