I've been looking all over the internet for the vacuum "motor"/actuator that controls the defrost duct. Finally after looking for two months, I've found a place that carries them still. The ACDelco part # is: 15-71578 but they discontinued production some time ago and I found the part on www.vpartsinc.com The GM cross reference # is 1996746. Today, they had 10 and I order 1 so if anyone is needing one of these, they should have 9 left.