Markers not alternating.
Reassemble.
Air in marker valve.
Bleed marker hydraulic system.
Marker valve defective.
Replace valve. See your John Deere dealer.
Obstruction in marker orifice.
Remove and clean orifice.
Marker lowers and disk blade is forced into ground.
Lengthen marker hydraulic hose loops.
Marker floats off ground.
Bleed marker lift cylinder.
Leaking tractor SCV.
See your John Deere dealer.
Marker cylinder not dropping down into J-slot. (Hose loop too short.)
Pull more hose out of frame tube and clamp.
Alternator valve defective.
Machine not lowered.
Make sure machine is completely lowered.
OUO1074,0000180-19-20060220