Mower blades not turning on

I have a craftsman riding mover and the blades will turn on very rarely. I cheeked the resistance on the clutch and it has resistance. But when i put the volt meter on the wire and the machine is running the voltage moves all over the place. Up, down to nothing and blades are still not coming on. If i drive the machine and turn one way or another it might kick the blades on but not always and when they do it turns off in a few seconds. I changed the PTO switch and a week or so ago it would run fine for about 20 mins then the blades would stop. I dont see any breaks in the wires but because some of the wires are not all exposed i couldn't check every inch. I thought about replacing the clutch but didnt want to do that and have the same problem. The clutch looks to original one form 2004.