Well, in the absence of anyone that knows speaking up...
I assume this is the valve behind the dash, correct?
The single is probably your incoming source line that may come from a vacuum canister under the hood. If so, it probably has vacuum all the time and you could easily check this.
The other three lines probably open doors within the a/c-heater box. Can you see any vacuum pods on or around that? Might be on top, behind or in front of the box somewhere. Just hook them up and see where you go - it's only vacuum!
Comparing this with my Duster, there is an incoming line; the heat line operates a pod that operates the valve in the heater hose line. The other lines operate doors in the a/c-heater box.
HTH
C
