How do the factory systems work? How do I figure out what is wrong? I can not find wiring diagrams for it or FSM diagnostic procedures or anything in alldata.

It won't even attempt to set, the diaphragm looks new, everything in side the thing looks new, it is getting plenty of vacuum (about 15" @ 55 mph) on one of the wires I get power when I put the switch in the on position, power to another wire when I press the set button and the 3rd gets power when I hit resume, the cable has to be ok because the speedo works and the cable runs through the cruise unit.