640 Draft Control Operation.

I am not sure my draft control is working properly.
If I am in touch control and lif an implement 1/2 lift.
Then move the lever down to Draft Control implement
drops to ground.
If I then lower touch control and then raise
it the implement starts to rise. And can be set.

By setting it after it is in Draft mode should it operate?

What sensing is done on the Hydraulic spring to
the top link?

Is it just measuring the tension caused by pulling
the plow when it is in the ground?

And using a stone rake would not work?
 
Corvetttteguy,
I was always told to only move the Hydraulic selector lever when the lift arms were in the lowered position.
You are changing the linkage inside to switch modes and that is best done lowered.

My understanding is that the draft control mode senses pushing AND pulling on the top link. (a plow pushes)
The system tries to maintain a constant force on that link. For light work, you have to have the control high up on the quadrant.
Also there are 2 places to attach the top link to the tractor. The lower hole is for heavy draft work. The upper is for lighter work / more response.
HTH
Keith
 
When the top link pushed with enough force to compress the big spring, the draft control plunger is pushed into the internal linkage, providing a lift command just as if you raised the touch control lever. At what point this action occurs, depends on your initial setting of the touch control lever & the compression force on the spring. Generally that force is substantial, but I have seen where just my hand force would result in lift (I would say incorrectly adjusted).
 
In draft control, lever down, you basically have three positions, lower, hold and up depending on the position of the touch control lever. These position will very depending on the draft on the big spring. And inch travel of the touch lever is a big difference. In position control, lever forward, the lift arms correspond to the touch lever position, and the big spring as relatively no effect.
 

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