Vacuum switch ID

[gchemist]

I was working in the engine bay cleaning up some wiring. Wires are being covered in flexible black tubing. I found a vacuum switch near the firewall fusible link. Anyone know what connects or runs the switch? The wiring is intact. The other end has a vacuum hose. I don't know where the vacuum hose connects. If I put vacuum to it, I can hear a click inside the firewall. The click is audiable with no key in the ignition.
I'm leaving it disconnected until I find where it goes. It may be part of the washer fluid system. I have no idea.

I did manage to fix the radio today!! Now I can listen to music while driving!!