One of the hoax motors won’t quit running
 

Acquired 97 986. Hvac not working. Control unit on but no snow flake, fan lights to the top but doesn’t blow, something is running under the dashboard whenever the key is on. I think it is one of the hvac motors( blend door...). Very puzzling.

The Boxster air boxes are notorious for loosing foam on the flaps that are actuated by motors for hot and cold air manipulation. One of your flaps is stuck and the motor that is trying to open/close it runs. I have the same issue, it’s not a big deal. If your HVAC is not blowing the proper air then your airbox needs to be pulled and repaired or replaced. IMO repair is the better option. Don’t assume your HVAC isn’t operating because portions of your HVAC display don’t show, the displays are known to fail, sometimes in very random ways. You need to check when driving to see if your systems are working or not. Both fixes are relatively easy DIY projects if you are reasonably handy.

Check out this link.
http://986forum.com/forums/performance-technical-chat/42802-interior-vent-debris-4.html