It seams my 3000 had 2 wires in both fenders as well. One was a warning flasher, the other a running light. Rear lights had 2 elements. If you have the flasher on the light switch, switch to that position, measure 12v between wire and a good ground, will show intermittent. Had lots of electrical problems with that tractor, ( think it was used in water ) cleaning up the ground wires solved most of them.
Chris