There is no running process can could possibly interfere with the fans this way. Besides that, they stopped working regardless of whether I boot into Yosemite or back to my original Mavericks partition.
Whether it's an SMC issue or else, it happened during the Yosemite install. There was a moment during the install when it updated the SMC to a new version and since then the fans have become rendered permanently disabled.
Have you tried restoring to Mavericks?
Boot to your Diagnostics test.
http://support.apple.com/kb/HT5781
Does that pass?
Boot into Safe Boot mode (Restart while holding the Shift key)
Can you run the fan utility (and control the fan) while booted in Safe Boot mode?
I think you may have shot yourself in the foot! (screwed the pooch, etc, etc)
(Now you know it is a really bad idea to try a major install on batteries only 🙁 )
I suspect that you have a corrupted SMC update, which may not be repairable, without replacing the logic board.
I have not seen a firmware update that would start without warning you that the power adapter needed to be attached.
Be sure to try the SMC reset again - double-check you are following the exact steps, as outlined in this article: http://support.apple.com/kb/HT3964
and - I'm out of ideas.
Take it in for service. (An Apple-authorized service shop or Apple store has other factory tests that MAY have other, potentially good, results, such as "kick-starting" (individually testing) the fan.
I had this problem a while back (much before Yosemite) and I fixed it by resetting the SMC. http://support.apple.com/kb/HT3964?viewlocale=en_US&locale=en_US Use this guide to help you how you do it.
I also put up my laptop after resetting the SMC holding it in front of my AC, and I guess either the air coming from the AC or resetting the SMC helped re-run the fans. It started working by making a weird noise at first but then went back to normal. It's been working ever since. Try this before taking it to repair and paying for it.
Let us know how it goes.
Tried resetting SMC, nada. Appointment booked... should be covered by the warranty considering it's a public beta, right?
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Should be a warning stickied in this forum or the official beta thread warning that due to a possible SMC update included with Yosemite, one should have it plugged to power despite the installer letting you proceed otherwise.
I have the same "problem" and I created a report. Personally, I would wait for the next update or even the final version. It is a beta and stuff like this is related to it so give them the chance to fix it.
Just before logging off tonight I noticed my core temps running high (Mac Pro 4.1-5.1 OSX10.10 beta, 12 core X5670's) and my fans were at idle, don't normally see my temps go over 60c and the fans be at idle, manually ramped them up with istat which brought the temp down straight away so that mirrors what you guys are saying??