I have a 2005 6520 4wd with only 120hrs. Just recently when i was doing some digging i noticed my RPM's needle start to bounce with no change in actual rpm's. Then the needle went to zero and then the oil pressure light came on. It would come back up again and the light would go off. This cycle would continue. Could the problem be with the instrument cluster. I say this because the tractor runs fine. And another question where does the rpm read the rpms from. wheres the wire.