Vent, A/C, Defrost vacuum switch problem

I have a 1993 Mustang LX. I was working on the A/C fan, vent cluster and heard a little hissing noise. Now when I turn the A/C on it blows through the defrost and heat vents, it won't switch to the dash vents.

I assume I lost vacuum on the switch. Can anyone tell me how to fix this problem. I tried tightening the nuts on the vacuum hoses but no luck.

Thanks for any help.

P.S. It was working before I heard the hiss noise. I was working on the hot/cold switch at the time. The plastic clip that slides the wire is broken.
Would it be better to just replace the whole cluster?