Having similar fan problems with 2 of my 3 with factory standard PSU. However as there is one machine running at full speed, I'm amiss to think that the PSU's cannot provide enough power, as the 3rd one wouldn't mine at 200Ghs+.
Even taking the chip frequency down to 300 doesn't cause the fans to start.
Strangest behaviour is that from a cold start, machines and fans work fine. Problems start once they reach working temperature.
What fan speeds are you seeing on your units. I am getting 2880 rpm on the upgraded power unit running at 1500 mhz. My other three units with the factory power supplies just can not keep the fan speeds up and I an running them under clocked until my other eight upgrade power supplies arrive. They are all running fan speeds at about 2280 rpm, if I raise the mhz the fans speeds drop and eventually quit due to the weak factory power supplies! One is still sitting cold just our of the box, waiting for the power supplies to arrive.
Mtnminer
Just wondering what is the best setup of fan speed that everyone is going for ?
Me after 3 weeks with my machines, the best combination for me is:
Chip Frequency(Default: 300) 1300 or 1400 (1500 drain too much energy, and increase the % of error too much so no point
Target Temperature: 65
Overheat Cut Off Temperature: 75
More Options(Default: quiet): --avalon-fan 20-20
These setup are giving me:
Temp1: 25
Temp2: 65
Temp3: -1
Yep, there's no way you're going to be able to run at 1500 with those temps at that fan speed. If I don't do anything to the fan speed, I'm at 29 and 41 and I can run 1500 no problem with about 4% error, which is perfectly fine.