If your overclock is too high the hash board will crash and give you a 0 reading, just go into the overclock settings and lower the setting and hit apply and the miner will restart with the new settings. Some people will start at 650 and go up step by step until it crashes. Keep in mind that when ever you get close to the sweet spot it might still crash. For instance mine will run at 675 for about 6 hours then one of the boards crashes. At 668 it will run for 12 hours and crash. Best setting for mine is 662 and has been running stable for 6 days with out any problems. I have a batch 2.

Also unscrew your fan and reverse it so that it pulls air instead of pushing the air. Mine went from 60c to 50C. I also run the fan at 55% instead of auto fan. results may vary depending on your ambient temps. Mine is in the basement where its pretty cool all day long so just keep an eye on the temps during the day and adjust your fan speed accordingly. I ran all of my miners at 50-65C.

hope this helps.