john deere blade clutch will not engage

 I have a 10 year old john deere sx38 lawn tractor. Over the last year
intermittantly the blade clutch has become disengaged suddenly while
cutting the lawn. When I try to reengage the blade nothing happens. The
engine keeps running it is just the blade that becomes disengaged. Then
it suddenly start working again. Today it stopped working and I have
not been able to get it to reengage.  When I pull the electric button
to engage the blade nothing happens. I don't hear anything.The electric
to the clutch appears to be working ~2amps.

Thanks in advance for any sugestions.

Regards,

Warren