Thanks for the link there. Perhaps some of us could use a proper fitting univeral check valve since most of our rigs are now certainly out of warrentee??? And even if some of you aren't getting the entire change from this vent to that, I think at times there is enough of a small leak in most of these systems to change the outside, inside blend and start letting in ourside air when not wanted enough to keep AC from being as cold as it could be and letting in other things from the outside as well. So I might suggest a check valve for all of us manual HVAC WJ'ers... Thanks again for the link. That is a great source... Need to check there more often...
