iMac's engine whirrs on and off whilst asleep!

[Frances144]

My iMac is 3 months over its one year warranty date, obviously! (I must check to see if I did purchase AppleCare or not, can't remember).

Anywho, when the iMac is asleep, the screen stays dark and the little light flashes to itself and that is fine.  But every so often a motor starts to whirr and then switch off.  The screen still stays dark.  What is that?  Should I be looking into this or is it all perfectly normal and I have only just noticed it!

Cheers
Frances

[chriskleeman]

Frances, my first guess would be an internal cooling fan. Normally, most computers that are sleeping don't generate too much heat, but it's possible that you're machine is getting just warm enough on the circuit boards that the heat sensor is turning the little fan on.

Now someone may come along and know it there actually is a cooling fan in your particular version of the iMac, but that would be the first thing I'd think of!

HTH,

Chris K

[gunug]

I don't know what you have either but I'm guessing it must be either a iMAC G5 or an iMAC Intel original version.  I think both of them had problems with the fan going on and on when the the machine is asleep or in "single-user mode" because the fan drivers either don't work right or they don't exist (as in single-user mode) so the fan goes full speed because it has no feedback from the thermostat on the logic board.  I think there are firmware updates that fix this on some models and I'll try to check this if you'll say what model you have.

[Frances144]

Thanks - my model is:-

Imac5,1
Intel Core 2 Duo
2.33 GHz
1 processor
2 Cores
4MB L2 cahe
2gb memory
667 MHz
Boot Rom version 1M51.0090.B09
SMC Version 1.9f4
Serial No CK6500UQVUW

Is that enough info!!?

Cheers
Fx

[gunug]

There is a large sequence of things that try to isolate noisy fans but they involve opening the
thing up and if it's in warranty you probably shouldn't! I realize that you're in the Shetlands so it might be
away from you for awhile if doing one of these two things (they are slightly different) doesn't help.  

Something to try:

1. Shut down the system.
2. Disconnect the power cord and wait 15 seconds.
3. Reconnect the power cord and wait 5 seconds.
4. Power on the system.

In some cases you might need to reset the SMC which is an auxiliary processor that controls things like
the fans and the power (note, I generally simplify things by starting with any extra peripherals unplugged).
 
Reset for the SMC:

1. From the Apple menu, choose Shut Down (or if the computer is not responding, hold the
power button until it turns off).
2. Unplug all cables from the computer, including the power cord.
3. Wait at least 15 seconds.
4. Plug the power cord back in, making sure the power button is not being pressed at the time.
5. Reconnect your keyboard and mouse to the computer.
6. Press the power button on the back to start up your computer.