Corrected previous homeowner's vendor installation. Found blower housing was installed backwards (reversed causing backflow), made correction and installed new 5" round metal ducting. Ordered new Jenn Aire Damper #A405 from Appliance Pro Parts on Monday morning, 3/2 and received it Tuesday afternoon, 3/3 with their normal shipping. Thanks for the quick service! Had to cut two holes in shelf, one to connect to blower housing from under the shelf and the other about 2' feet away to bring back up to the top of the shelf to vent through to the existing exterior opening. Used 4 - 90 degree adjustable elbows and cut 2 - 60" round links to fit my installation. Used self tapping sheet metal screws to secure the connections and then sealed them with 3M Aluminum Duct Tape. Now our unit has a clean, space effective installation at the back of our cabinet that resulted in about 25% more shelf space, and our Jenn Aire Downdraft now works as designed!