I'm guessing that what you are seeing on the used combine may be the original Truesight steering controller system. I have a Truesight 2 system in my combine. I'll attempt to explain how my Truesight 2 works and speculate how an original Truesight (I) might work.

My Truesight 2 steering controller is used for corn harvest only. It has a set of feelers which I mounted on the corn head. These feelers "feel" between the inside of a pair of rows. I have an 8 row head and my feelers are attached to the snout between rows 2 & 3. A wiring harness runs from this sensor to a disconnect point between the corn head and the combine. When I disconnect the corn head, I disconnect that connector so the feelers/wiring stay with the corn head. No other wiring is distrubed.

There are sensors on the combine itself including a head height tee, a steering axle position sensor, a seat safety sensor and maybe some others. In operation, the feelers along with the other sensors send control signals to a steering device. The steering device can be a hydraulic steering valve that came with or has been added to the combine OR a steering wheel turning device such as Ag Leader's Steady Steer motor, OnTrac, EZ-Steer or others.

During corn harvest the feeler system runs the steering device. In other crops, the original steering controller could but doesn't have to steer the combine using AB lines based on GPS.

When I harvest soybeans, I use my InCommand and my Steady Steer controller to control my Steady Steer motor on the steering wheel. This would be 100% an Ag Leader steering system turning the steering wheel on my Deere 9770. The steering is done based on AB lines from planting or new AB lines I create at harvest.

When I harvest corn, I disconnect the Steady Steer motor from the Steady Steer wiring and plug it into the Truesight 2 wiring. I also disconnect and move the connection for my engage button from the Steady Steer System to the the Truesight system. This is extremely easy.

It is necessary for the operator to have some input to the Truesight system from time to time as far as setting up the system and fine tuning it. With the Truesight 2 system this could have been done with a separate control box/display from Truesight. Instead I chose the option where these inputs are handled through my InCommand screen set to view the Universal Terminal. This does cover up part of my InCommand screen but is only used when starting a field to override the safety feature and to make rare adjustments. In normal operation, the UT screen on the InCommand is not shown.

I am very happy with this combination. The InCommand handles yield monitoring and steering through the Steady Steer controller and motor in soybeans. In corn, the InCommand handles yield monitoring and allows interaction if needed with the Truesight 2 system. The Truesight system controls my Steady Steer motor. This allows my Steady Steer motor to steer the combine in either crop.

What I have described is my Truesight 2 system and how it works with my combine. What you are seeing could be a Truesight 2 system using the standalone control box/display or an original Truesight system.

I have no experience with the original Truesight system.  My guess is that the concept is the same where the Truesight system uses its feelers to control an existing steering device (hydraulic valve or steering wheel motor) based on feelers on the corn head.

If the used combine has a Truesight 2 in it, I would consider it a positive feature as it does work well. If the combine has the older Truesight in it, I would consider that as less of a positive although it might work fine.  You do not have to use it.

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