I was at a school and they have two sensor racks and both were throwing big hissy fits. They both were in desperate needs of cleaning. I did try to clear the errors with the doors open but i cannot remember how to reset the errors. I though you just pushed clear or reset to clear the errors, but it has been a while since i have played with the CEM's. I pushed clear, nothing happened, so i pushed reset, the CEM reset but gave me the same errors, they were air flow, rack over temp, dimmers xx, xx, xx.... over temp, and backup mismatch. Most errors i have seen on a rack. My button pushing finger was getting sore scrolling through all of the errors. I am going to go in next week or the week after and do a full maintenance cleaning on both of their racks. I will have to schedule some time for their theater to be dark since the dust is so caked up i will have to shut down the racks and suck as much dust out as possible then blow the rest of it out. I figured the rack wouldn't throw a over temp error if there wasn't a load on it and the room temp was rather cool.