ok so ill get to the point here i have an 84 camaro and my fan is stuck on vent so its not a vaccum problem (i think) because normally it would go to defrost with no vaccuum and the fan will only work on low and high and i put a new relay in for the blower so if anyone got and tips of whats causing this thatd be just dandy

 

It is a possibility that the control valve on the back of your a/c unit is stuck. Its a disk shaped part that is held in place to your unit by two screws and it has the connector on the back that the vacuum lines plug into. I'm not sure if you have a non-a/c unit or an a/c unit. Either way the valve has a rubber disk inside it. Its possible that the prong(it holds the disk in place when you move the selector) on your rubber disk has broken. I just order one from Rockauto, a/c style for $12. Another possibility is that your vacuum "motor" is stuck to its position and the vacuum will not release to close the damper door. I also just order a vacuum "motor" for my defrost duct. Check out the thread "Good info for you guys" just post a few days ago.

 

Alright thanks and actually i just fixed it at 8:30 this moring during school i had it all apart in the shop and i was messing around with that donut and the vaccum line and i just pushed on that donut and the line starting making the clank noise of the doors opening and it started working. So im kinda glad its working now but in the same way i wish i new what i did incase it goes bad again.