I should also have said (between #1 and #2) that anything touching the mat on the "C" side would cause the behavior as well. And, that I believe that a defective "C" motor is unlikely - only mentioned because it is possible. What does your drive train look like (simple wheels, simple treads, or a complex mechanism) and what contact with the mat is there besides the drive mechanism. One year the team didn't do a good job of setting the height of attachments (or initial placement), so they dragged a lot, but with no constancy. As a result, they never knew which way the robot would go because the controller frequently couldn't compensate (and they had a pretty simple drive mechanism) - they ran into alot of stuff and subsequently didn't score well. Brian Sent from my iPhone On Nov 1, 2013, at 9:37 AM, Rahman Rasulzada <[log in to unmask]> wrote: > <Presentation1.jpg> > Here is the what we are having problem > > > On Fri, Nov 1, 2013 at 8:30 AM, Rahman Rasulzada <[log in to unmask]> wrote: >> Hello folks , >> >> We are having a trouble with new Ev3 large motors. Robot wheels not going straight however they put same values (rotation or degrees) but robot degree values change automatically... My students reset , and updated firmware but still having same issue. Motor values keep change ........ >> >> Any suggestion ? Really appreciated >> >> >> -- >> _________________________ >> best regard, >> >> Rahman Rasulzada >> Pinnacle Academy , >> IT Manager & Computer Teacher >> School Website >> Personal Website >> Computer Classroom Website > > > > -- > _________________________ > best regard, > > Rahman Rasulzada > Pinnacle Academy , > IT Manager & Computer Teacher > School Website > Personal Website > Computer Classroom Website > > To UNSUBSCRIBE or CHANGE your settings, please visit https://listserv.jmu.edu/archives/vadcfll-l.html and select "Join or leave the list". > VADCFLL administrative announcements are sent via VADCFLL-ANNOUNCEMENTS-L. Visit https://listserv.jmu.edu/archives/vadcfll-announcements-l.html to subscribe. -- To UNSUBSCRIBE or CHANGE your settings, please visit https://listserv.jmu.edu/archives/vadcfll-l.html and select "Join or leave the list". -- VADCFLL administrative announcements are sent via VADCFLL-ANNOUNCEMENTS-L. Visit https://listserv.jmu.edu/archives/vadcfll-ANNOUNCEMENTS-l.html to subscribe.