The 242 case never had a vacuum switch on the transfer case, it also never had a CAD front axle. It is a standard electrical switch with 2 wires, black/red used only by the 242 for the full time light. The other is grey/yellow switching to yellow/black after a connector that is used for the part time light. The ground for the lights is through the body of the transfer case an added a ground strap to the transfer case would not be a bad idea. These pics are from the '87 Comanche electrical schematics and parts diagram part 24 on the diagram.