I just read an answer post you had made in response to a question about a 2003 Chevy Astro van vacuum line keeping the vents from switching from defrost to floor, to dash vents, etc., you mentioned changing about 2 a week. How right your were! This is oustanding information. I think it's a 1/8" hose tagged 22 at the plastic "T" fitting. I have a 2003 Astro with the same problem. One more question for you, the hose is britle, dried out and breaking, I can't seem to reach were it attaches closer to the drivers side. Happen to know what it connects to? Thank you!

I didn't initially answer your question, or even read it but I know what you are talking about. The source vacuum to the HVAC system inside the van. It attaches to a vacuum port on the left side of the engine just above valve cover attached to a bracket. They are very brittle plastic and break easily. I found it better to replace the vacuum line with small rubber line, such as washer fluid hose. Its easier to route and can be installed without bending plastic. Feed it from the left side vacuum "T" above the left valve cover, over to the heater valve on the right side in heater hose split. Its the source vacuum to inside, and if lost it defaults to the defrost mode and won't change modes.