So I pulled out my heater box to replace my leaky core. I had noticed a wire sticking out from it over the summer and never gave it much thought And forgot about it.
turns out it was a makeshift control for the damper. The vacuum control seems to be ok so I assume there is an issue with the hose going to it? Where should I start to troubleshoot this

 

Wow,that is one way to get the door open.
I would start at the vac control switches on the climate controls along with vac lines and then keep working your way out. Maybe accumulator?