OK I removed the monovalve and the rubber insert looks good as far as I can tell.
I checked the power coming into it. There are 2 leads. In Defrost mode both leads had power, while in all other modes only one lead had power. This is with temp wheel max cold and max hot. I am going to drive around today with the power disconnected just to see.
Anyone know what these readings point to? Are they normal signals sent from pushbutton unit? I dont want to replace the monovalve unless necessary ($145 for monovalve, no repair kit or insert listed).