Electric Clutch want engage the mower deck on my l120 john deere lawn tractor. all of the belts are ok.

They wear out. How old is the mower? Mine just gave out this week in the peak of hay season. (my grass) The wire can be unhooked from the PTO clutch and a 12 volt jumper can test it, if it jumps, it is good, if not, it is shorted out, they are expensive, I found 3 of them all the wrong size for mine. Try to find the same one. Ebay has a couple on there right now. Check it out.