Small Engines (Lawn Mowers, etc.): Lawn Chief #440 riding lawnmower wont turnover, safety switches, lawn chief

Question
I have cut the lawn 3-4 times this year--no problem.  Now-it won't turn over.  It's a key start but no noise at all when I try to turn it over.  I figured it was the battery (3 years old) so I replaced it.  No luck.  Still no noise and it will not turn over.  
There is a "seat switch" on this model, but I can't get to it even if I knew what to do with it! The unit is about 7 years old and has been a wonderful lawn tractor.  No problems until now.
Any suggestions would be GREATLY appreciated--the grass is getting long!!!

Answer
Hi Bill,

You will need to trace the wiring from the battery, through the key ignition switch, to the solenoid and finally, the starter.  Include any safety switches like the seat and also a blade engagement switch.  Even if you can't get at the switch, disconnect its wires and bypass it for testing purposes.  You can also do some test jumpering, like running power from the battery to the starter to see if it turns over or to the solenoid to see if it sends power to the starter.

Let me know how you make out.
Michael