Your extra wire is probably for an hour meter or light if it is connected to the switch. Chances are the witch is bad. or you have a broken wire between switch and generator. Your switch is a double pole, double throw and the stop and start circuits are paired. IF you do not have your owners manual, one can be downloaded
http://www.generac.com/genImages/bg/pageBG.jpg
Good luck and keep us posted.
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Mike, Certified Master RV Technician
Amy, RV Merchandiser; Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser & 2 toads