iMac internal fan

[lacker]

HELP PLEASE: Fan running very high speed immediately when startup bottom pressed -- cool 14.1 C. inside house, MacHD showing 28 c. in Dashboard widget after several hours of running. Exhaust air is cool.

"fan" DASHBOARD TEMP report says "no fan sensors found" (but we think it may have always said this)

What's happening?
And what to do.
And is immediate attention needed?

loren and sandy
Mid-2011 iMac12,2 / 27" / Intel Core i5 / 2.7 GHz / 12GB Ram / OSX 10.9.5 “El Capitan" /serial number C02FMGNWDHJP

 

[TimRichards]

Did this ever resolve? I have an iMac - same problem - took it in, they said "new motherboard"... I use it just as a secondary screen, runs fan program to control the fans - an article I read suggested a sensor problem on the motherboard might be at fault; slightly beyond me to fix but the fan app controls the fan ok as a workaround.

 

[chas_m]

This is actually likely to be a false report from the so-called "fan management" program, and the problem is likely caused by this as well. Macs do not need "fan management" -- they were designed with such things built right in. I would recommend uninstalling the "fan management" program and see if that fixes the issue. In the extremely rare event that the fan genuinely isn't working, Byte or another Apple-authorized dealer can fix that issue either under warranty or out of warranty, depending on the situation.

IME as a former Apple tech, 90 percent of the time we got this problem for repair the issue actually turned out to be the fan was in serious need of a good cleaning (ie dust buildup). Possibly get some compressed air and see if that helps.