My 94 3500 cube van has a vac can right next to the washer solvent tank. My cruise is not working and the line from it goes to the vac can. But the other port doesn't have a hose hooked up to it. Where is it supposed to be fed from. There is a switch just to the left of the vac can with one vac hose and I was wondering what it is for. Thank's for your help!