Try download this package https://feeds.braiins-os.org/am1-s9/firmware_2018-11-27-0-c34516b0_arm_cortex-a9_neon.ipk and install it from the web ui or via ssh:


The latest firmware is supposed to be able to control the fans, did you check they were set correctly? Also see if you have set chip voltage and frequency settings in that particular miner and try if letting it auto adjust works better.