Small Engines (Lawn Mowers, etc.): John Deere L120 PTO will not engage, john deere l120, safety interlock

Question
I have a problem that is making me crazy!  I have a 3 year old L120 that the electric PTO will not engage while the engine is running.  With the engine off but the key in "run" position, you can hear the electronic clutch engage/disengage when you pull/push the PTO switch.  Start the engine, sit in the seat, pull the PTO switch, nothing.  Lift off the seat with the switch out and engine running the blades start to turn while the engine is stoping. I have replaced the seat switch, the ignition switch, the PTO switch and the safety interlock relay to no avail. Still the same problem.  Any thoughts on this one  

Answer
 Hello David:

 Are you Sure that the PTO isnt Slipping when the Engine is Running and is Grabbing when the Engine RPM's Start to Slow Down? From your Description it Sounds like the PTO Clutch is Slipping. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. I enjoy knowing the Outcome. Thanks.

 Good Luck

 Respectfully

 John