Just bought a used Craftsman ZTS 6000 zero turn mower and it cut great first time I cut. a week later when I tried engaging blades there was a clicking sound like a relay making but the clutch never engaged with drive shaft. yes, the safety features were all in place and the belt in place properly, etc. All three blades will spin freely by hand with mower off, so no obstruction below deck. I checked all wire at connectors and no apparent corrosion. New battery, etc. It clicks every time I pull the engage switch, so apparently the switch is okay as well. Does this mean I will have to replace the electric clutch? or could something else be the cause? thanks in advance for any help.