Small Engines (Lawn Mowers, etc.): Craftsman snow blower auger/traction interlock, field service technician, manufacturing engineer

Question
I bought this machine brand new in 2001 and at that time the interlock system worked perfectly. Recently the interlock system failed to work. There is nothing in the manual about adjusting, fixing or parts. When I contacted searsparts direct they could not help me but directed me to another of their repair sites. This site could not help me only offered to set up an appointment with a field service technician. Being a retired manufacturing engineer and on a fixed budget I prefer to perform my own repairs. Any assistance that you can render would be greatly appreciated. Thank you. Joe.

Answer
What is the model number of the machine?  The model nubmer will be on sticker, about the size of a business card, usually located on the rear of the machine or under the handle or drive cover.  The model number format will be similar to xxx.xxxxxxx

Rarely do the manufactures provide schematics for outdoor power equipment.  This makes it challenging to identify which circuit is what as well as if a switch is normally open or closed.

How did the interlock use to work?  If you released the wheel drive or blower auger would the engine stop?

Have you traced the wires from the handle to the switch or switches?  

Eric