My Sharp AR-336 copier gives two error codes: 1)is F2-37 & 2) is U2-00. The U2-00 I can clear everytime. The F2-37 won't clear for hours. The only things is to leave it unplugged for several hours then try again. Sometimes it takes several attempts to reset the F2-37. I have paid for 3 service calls and no one seems to be able to fix it.

When you turn on the machine it rotates and takes severaal readings from different sources. one of them is for the drum, adjusting the seperation to the age of hte drum. So as the drum ages with the amount of copies it automatically adjust it self. Have the tech replace that sensor (if they haven't done so) or maybe it just has toner on it giving false readings.

http://www.copier-help.com/copier-help/ecs/sharp/ecssf2216.html