Hi, I’ve been able to rebuild the heater valve myself and it seems to have worked fairly well. NAPA sells the diaphragm for about 10 bucks. It is part no. BK 6601000. You just have to pry the tabs away from the back and separate the parts, remove the old valve, clean up the pieces (I bead blast them), then I put some spray on gasket sealant and put in the new valve and put the pieces back together again as tightly as possible. Haven’t had a problem. Anyway, maybe I don’t understand your problem? Let me know and maybe I can help.