Grasshopper 721-D Switch Interlock Smoked and Melted!

I have a 1993 Grasshopper 721-D; Serial #333489. It was idling out front and all of a sudden the switch interlock module (184220) started smoking and melted and the engine died. I ordered a new switch and the mower worked for about 5 minutes, the switch smoked and melted again. I installed a third switch. Mower worked for awhile and when I parked it out front the engine died. May I ask what should I do to fix the problem?

Jim