Hello, I have problem with this error : "A1 motor overload" and I test my robot by cyclic movement between two points . Several times, the robot suddenly stopped and show the message “A1 motor overload.After resetin error with ackn all i can move it more but again error occurs. Please help 
My robot type: System KR5 sixx R650
KR5 C2SR FLR 650
A1~A6 don’t have load attached to the robot
Not sure what exact conditions are used to trigger that message for that type of robot. Normally overload is observed as motor current is too high for too long. this could be because of something mechanically wrong, or it could be faulty motor, cable, brake etc.
i used to repair some of those long before i got any documentation on them. at least now they are online and pretty much every document you see on Xpert is what what KUKA techs would use. Last time i played with one was few years ago. one of the wrist axes (A3 i think) had mechanical failure of the brake. electrically brake still worked and one could hear the click but mechanically shaft was not being released...
one thing about this robot that is relevant to this case is that A1 has no brake so robot must be mounted on floor or ceiling. this also means when not powered or when drives are not enabled one can move the A1 by hand. in this case that would be useful check to see if mechanically A1 moves easily. if not, motor would see that resistance as added load.
you can also try dismounting A1 motor and try to run it without any load. it is likely that you would still get same result. so better choice in my opinion is to check motor and able electrically. there is a chance that there is an insulation breakdown between windings and this would act as increased load and maybe only becomes active when motor reaches certain temperature.
note that for testing cables and motors normal multimeters are just not very good at this since resistances are in very low range. even multimeters with high resolution may only be slightly better.
either way goal is to get readings across every motor coil and compare them.
for low resistance measurements one gets much better results when using higher test current (100mA for example). this could come from external device and one can simply measure voltage drop.
old analog meters used to put up to some 100-150mA on x1 Ohms range but of course those are just not common any more. digital multimeters normally use 0.5V for resistance tests, and about 3V 1mA on diode test.
