First of all thanks for the great job you make here. You´ve helped me a lot of times with success. I´d like to identify each of the 3 fans inside my iMac. I run iStats gem and I can see three fans but wich one is the HDD fan, the ODD fan and the CPU fan? Below you can see the result:

--- CPU Stats ---
**CPU temp:               0.0°C**       ▁▂▃▅▆▇

--- Fan Stats ---
Total fans in system:   3           
Fan 0 speed:            998 RPM     ▁▂▃▅▆▇
Fan 1 speed:            1099 RPM    ▁▂▃▅▆▇
Fan 2 speed:            1198 RPM    ▁▂▃▅▆▇

--- Battery Stats ---
No battery on system

Additionally you can see the CPU temperature is 0. Why?

If I run iStats scan I can see too many unknown sensors and a extrange HDD temperature. Below the results:

Tm0p Misc (clock chip) Proximity: 50.94°C     ▁▂▃▅▆▇
Tm0P Unknown:           50.94°C     ▁▂▃▅▆▇
Tm1p Unknown:           55.25°C     ▁▂▃▅▆▇
Tm1P Unknown:           55.25°C     ▁▂▃▅▆▇
Tp1P Unknown:           54.38°C     ▁▂▃▅▆▇
Tp2H Unknown:           61.38°C     ▁▂▃▅▆▇
Tp3H Unknown:           55.75°C     ▁▂▃▅▆▇
TA0p Ambient temperature: 25.88°C     ▁▂▃▅▆▇
TA0P Ambient temperature: 25.36°C     ▁▂▃▅▆▇
TA0V Unknown:           25.25°C     ▁▂▃▅▆▇
TC0C CPU 0 Core:        57.77°C     ▁▂▃▅▆▇
TC0H CPU 0 Heatsink:    50.38°C     ▁▂▃▅▆▇
TC1C Core 1:            59.0°C      ▁▂▃▅▆▇
TG0p Unknown:           57.0°C      ▁▂▃▅▆▇
TG0D GPU 0 Die:         57.75°C     ▁▂▃▅▆▇
TG0H GPU 0 Heatsink:    56.0°C      ▁▂▃▅▆▇
**TH0O Unknown:           1.0°C**       ▁▂▃▅▆▇
**TH1O Unknown:           1.0°C**       ▁▂▃▅▆▇
TLAV Unknown:           44.16°C     ▁▂▃▅▆▇
TLBV Unknown:           40.94°C     ▁▂▃▅▆▇
TLCV Unknown:           42.05°C     ▁▂▃▅▆▇
TL0p Unknown:           50.94°C     ▁▂▃▅▆▇
TL0P LCD Proximity:     39.08°C     ▁▂▃▅▆▇
TL0V Unknown:           42.05°C     ▁▂▃▅▆▇
TL1V Unknown:           38.92°C     ▁▂▃▅▆▇
TL2V Unknown:           44.16°C     ▁▂▃▅▆▇
TMCD Unknown:           60.0°C      ▁▂▃▅▆▇
TO0p Unknown:           43.31°C     ▁▂▃▅▆▇
TO0P Optical Drive Proximity: 42.31°C     ▁▂▃▅▆▇
TPCD Platform Controller Hub Die: 59.0°C      ▁▂▃▅▆▇
TS0V Unknown:           40.05°C     ▁▂▃▅▆▇
TS2p Unknown:           42.63°C     ▁▂▃▅▆▇
TS2P Unknown:           42.63°C     ▁▂▃▅▆▇
TS2V Unknown:           40.34°C     ▁▂▃▅▆▇

Could you give some light?


  • Are you experiencing a problem with the fans, or with overheating? The trouble with things like iStat is that they provide far too much information, most of which is "normal"!
    – benwiggy
    Commented Apr 16, 2020 at 12:07
  • Shouldn't the CPU fan be the easiest to find out ? you just need to do a CPU intensive task, with nearly no disk IO. For example, a huge loop of big calculations Or compiling something . Also, software.intel.com/en-us/articles/intel-power-gadget can give a live temperature update (if it runs on such an old machine) which is proportional to fan speed.
    – anki
    Commented Apr 16, 2020 at 12:45
  • Fortunatelly I don´t have any problem with the fans. But I´d apreciate to distinguish each one of the fans. And to know why HDD temperature has this so low value.
    – Alicia
    Commented Apr 16, 2020 at 13:32

1 Answer 1


There is a free app called Temperature Gauge which may help you. This app will identify each fan. This app runs in the menu bar. So after starting you should see a new icon in menu bar.

  • Thank you And without external apps?
    – Alicia
    Commented Apr 17, 2020 at 10:13

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