Yeah, arbitrarily heat the temp sensor to at least 60C. If the fans aren't running full speed it's because it's not hot enough to need to do so.
The main regulator isn't directly cooled by those fans anyway so that shouldn't change much.
Also how are you getting over 130GH average when 250MHz peaks at 110GH? And then the fans idle down? That only happens when it's cold, and if it's cold it's not hashing at 120% theoretical max.
I think something is wrong because too much of what you're saying you're seeing doesn't make sense.
Sorry about being unclear. I am just going by what cgminer is outputting. What would help debug why one is having trouble over 200MHz?
I have had one running off a Pi at 250MHz for the last 15 hours that is now at an average of 82.45Gh/s but has 411 HW errors. No resets, still 0 GSE.
This is the one that was idling down the fan. I watched the CGminer output for a while last night but didn't see any correlation between the work/difficulty or pool when it happened. Yeah, should not happen as they are still hot and hashing. The auditory pitch change from fast to slow sounds like slower than when the unit is idle. Is fan speed output on any debug channel?
The other is running stable at 200MHz for the 15 hours off another Pi and 3 2pac.
This one can sometime get stable at 225MHz but has a lot of HW errors.
I am happy to help in any way.
EDIT: to note that I just noticed the cgminer output on the pi with one R808 is reporting COMPAC-6 now.
Here is a screen shot
https://imgur.com/mVJ6xuA