Fan speed jumps then returns to normal.

[Alex]

I set HDD fan speed at a constant value of 3000. From time to time the fan will jump to what sounds like max RPM then return to my preset value. It only lasts about a second or two. Using latest version. iMac Mid 2010. OSX 10.9. Any thoughts?

[Steven]

Alex
Does it happen when the mac wakes from sleep ?

[Alex]

No. It happens at any time during usage. Web browsing. Netflix. Any time really. It does not happen every day but it has happened a few times within 1 hour. I thought maybe it was other left over files from previous fan controlling software but I have removed all those files and the issue still happens. Maybe the system control is trying to take over on its own? I don't use System or Sensor based value because they are too loud even with playing music. Anyway here is the tech info.

Macs Fan Control 1.1.11, iMac11,2, Mac OS X 10.9

Fans:
ODD-min{2000}curr{1998}max{4350}mode{0}
HDD-min{1100}curr{3021}max{6000}mode{1,3022}
CPU-min{1200}curr{1199}max{2600}mode{0}


TempSensors:
TA0P (Ambient) - 22.1992
TA0V () - 22.0234
TA0p () - 24
TC0C (CPU Core 0) - 39.3125
TC0H (CPU Heatsink) - 37.25
TC1C (CPU Core 1) - 47
TG0D (GPU Diode) - 45.75
TG0H (GPU Heatsink) - 40.5
TG0p () - 43
TH0O () - 9
TH1O () - 9
TL0P (LCD proximity) - 21.5469
TL0V () - 29.7227
TL0p () - 34.875
TL1V () - 25.9023
TL2V () - 28.5117
TLAV () - 28.5117
TLBV () - 25.4258
TLCV () - 29.7227
TMCD () - 47
TO0P (Optical Drive) - 28.75
TO0p () - 29.75
TPCD () - 59
TS0V () - 28.8828
TS2P () - 30.625
TS2V () - 28.332
TS2p () - 30.625
Tm0P (Mem Controller) - 39.25
Tm0p () - 39.25
Tm1P () - 41.5
Tm1p () - 41.5
Tp1P () - 53.625
Tp2H () - 66
Tp3H (PSU Primary) - 47

[Steven]

Alex
It must be some other fan controlling software, that's the only idea I have