Okay...I've tried to find the answer here. If I missed it, I'm sorry.
With that, my 1985 z31 NA is no longer blowing air into the cabin. Here's what I know.
The previous owner (my brother) had some problem with the blower. He took it to a shop and they "fixed" it by making the blower run full speed all the time.
After I replaced all the underhood vacuum lines and the main feed vacuum line under the the dash, the blower fan no longer works.
so...
1. Does anyone have any idea what was done to make the fan blow at high speed all the time?
and...
2. Is there a vacuum diagram for the underdash/cockpit climate controls?
Thanks!
3. She's running strong now because of the info y'all gave me on this forum.

 

Take out the blower fan driver amplifier. Open the plastic case. There is a little silver strip that desolders itself as a fuse. Resolder it. Then rewire the blower eires back to factory to correct the half cocked bypass that the shop did. You will have full speed control again.