Hi All, Anyone wondering what that little black vacuum hose connector is doing on the rear of a 68 skaylark htr/vent/ac/rec thumbwheel switch - its nothing more than an adaptor that blocks off the #4 port of the switch. If the adaptor rots out, you can go connect the vac. lines directly to the rear of the switch provided you make up a suitable block (piece of hose with a plug in it) for the #4 port. Regards Tonino