Do you mean your avalon fan is working in the first run and then sooner will stop?
What PSU you are using maybe the power supply lower than the miner do you have any wattage meter to check if ever your miner is running with 1150w.
If its ok maybe your fan is damaged If your unit still under warranty better to contact their support about your unit.. because its not good idea to open the unit to troubleshoot if what actually the problem if still under warranty only support of canaan can give you idea what is actually the reason of the fan not running ..
Someone also having problem about avalon but its totally dead avalon you try how he troubleshoot without avoiding warranty
https://bitcointalk.org/index.php?topic=2196951.0