New to us JD planter with a seedstar 2 monitor.  Everything seemed to be working good in a brief test a month ago but constant rain since kept other testing and use on hold until today.   Noticed today that the monitor which gets its speed from the tractors radar reads about 20 percent low and therefore runs the hydraulic drive a bit slow.  Tried the recalibration process in the monitor book a dozen times or more and it always ends with calibration failed.    Have done the math and know where to set the rate to compensate now and coincidentaly found out why the previous owner had the rate set where he did, but,  there ought to be a way to calibrate it to the right speed and can't tell why the calibration keeps failing. 

Just curious if anyone else had this problem in the past and found the problem.