Near Intersection of I-35 & I-90 Southern Mn. | My first auto steer was on my 8120 tractor.with ILS. It could have been ordered with Deere's steering but I had not done so. I had an Insight with a Trimble Nav II and external hydraulic valves installed.
The LS or Load Sense port was needed. The reason being Deere's decision to allow the hydraulic pump to destroke when there was no need for hydraulic flow. Inside the SCV stack there is a passageway with shuttle type check valves that "sense" when hydraulic flow is needed by one or several of the SCVs. The pump runs at a low output but gets "tripped" up when you use an SCV so you quickly get higher output. When using this area as the hydraulic source for steering a shuttle valve may be needed to cause the hydraulic pump to be ramped up for providing sufficient oil flow for steering.
My 8120 seemed to work fine in initial testing. When I went out to plant corn with the system I had my planter attached which I had not done with any testing. The planter was a Vac type so the Vac fan was needed at all times. This itself should have kept the hydraulics ramped up. My outside pass was near a drainage ditch so I was manually steering the tractor. I planned on using auto steer once I got the field started. As I carefully drove along the drainage ditch I felt the steering fighting me and I did not always have control. This was a bit scary.
I stopped, got out and disconnected the connectors leading to the external steering valves. I thought this should stop an problems due to the auto steer system. When I got back into the cab, I sat there and tried to think through the problem. It was then that I noticed that wheels started to turn by themselves. In an effort to get planting, we fashioned some plugs for the hoses and fittings on the connections to block off any flow through the steering valves. The tractor then returned to normal but without auto steer.
One thought was a problem of debris in the steering valve. After some investigation the problem was discovered. On top of the valve stack (there are a couple of different styles) there were some ports. LS was stamped in the cover close to a port. The installer had misinterpreted which port was which. He had fed the small hose that was supposed to be for Load Sense to an incorrect pressure port. This caused the oil to go "backwards" through the external steering valve which was then turning the wheels even if the external steering valves were electically disconnected. This occured when the Vac SCV was ramping up the flow. With the Vac SCV off, the steering worked properly. Once the Load Sense hose was connected to the actual LS port things cleared up.
Later an 8310 had a similar system installed. The cover on the valve stack was the same general scheme. They provided four different sized orifices for the Load Sense arrangement. I believe they gave some directions as which to use based on the valve stack. The correct was chosen and that tractor steered fine right away.
Both these tractors were steered this way for several years. This year I traded in the Insights and Nav IIs toward InCommand 1200's and SteerCommand. The external valves did not need to be changed. The SteerCommand harness was plugged into the valves and after being calibrated work well.
My guess is your problem might be like mine in that Load Sense is not getting tripped up properly since it seems to work when an SCV is operating which is apparently ramping the flow up.
Edited by tedbear 3/23/2018 10:09
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8300 ag leader steering problem
