Oct 23 2012
After a few days away from my iMac I returned and powered up and the fan was on full blast for no reason, and my temperature gauge (i use iStat Menus 3) was blank .. weird! So I googled around hoping to find a solution that didn’t involve bringing this machine in for geniusing (although it is due for that hard drive replacement I was notified of last week.. ). What did I find? an apple kb article that suggested a series of restarts to see what the problem is and possibly restart the SMC (system management controller) ..
Before Resetting the SMC
Try each of the following steps in this order before you reset the SMC. Test the issue after completing each troubleshooting step to determine if the issue still occurs.
- Press Command + Option + Escape to force quit any application that is not responding.
- Put your Mac to sleep by choosing the Apple () menu from the upper-left menu bar and then choosing Sleep. Wake the computer after it has gone to sleep.
- Restart your Mac by choosing the Apple () menu from the upper-left menu bar and then choosing Restart.
- Shut down your Mac by choosing the Apple () menu from the upper-left menu bar and then choosing Shut Down.
If the issue is still not resolved after following the troubleshooting items above, an SMC reset may be necessary.
- Shut down the computer.
- Unplug the computer’s power cord.
- Wait fifteen seconds.
- Attach the computer’s power cord.
- Wait five seconds, then press the power button to turn on the computer.
This fixed my high speed fan and no temperature reading! Hopefully this helps some people who may have fans running non stop on their iMacs. I am glad it wasn’t a hardware issue – and now I know a little more about the SMC.