I'm under my dash to replace my heater core and I see this. its something vacuum controlled and from the looks of the vacuum boot it doesn't work right now. I'm going to replace that boot but I don't even know what to ask for. anyone know what this is? under dash by ecu

 

Its one of the vacuum valves that control the HVAC doors.

 

my a/c is working but it does take a bit longer to switch vent locations than I think it should. I will replace it and hope that makes it better. maybe I can get everything under the dash freshened up while I'm in there for the heater core. because I DONT want to go back under the dash if I can help it.

 

I'm not really seeing a problem in the photo. The doors inside the HVAC box tend to get sticky from leaking heater cores that were never cleaned up, rust, the foam rubber turning gooey and sticky from age, and so on. Slow response could be from any of the above, or a slow vacuum leak.

 

if you look close at the boot at the end of that vacuum hose its ripped. I'm sure I have a vacuum leak here. Its the boot on the end of the orange vacuum line on the a/c that connects to the recirculation diaphragm.