Please help me stop the CPU fan noise on my iMac
The noise usually starts within the first 10 minutes of usage but sometimes it can go noiseless a bit longer.
Activity Monitor shows no heavy processes running to justify the noise (no Spotlight indexing or anything) and the temperatures are as low as can be.
Usually putting the Mac to sleep and waking it up slows the CPU fan down, but it will go nuts at 3900 rpms soon again.
Once the CPU fan has spun up to its max it never spins down again unless the iMac is reset or put to sleep. Even after hours of useless fan spinning has left it freezing cold.
Machine:
iMac (Early 2008) Intel Core 2 Duo 2.66 GHz, 4 GB RAM
Main OS: Snow Leopard (fully updated)
Boot Camp partition running Windows 7
iStat Pro stats:
Optical Drive: 999 rpm
Hard Drive: 1272 rpm
CPU Fan: 3899 rpm <-- culprit
HD : 50 (degrees celcius)
CPU: 33
GPU: 40
CPU 97-98% idle
I have already tried the following to no avail:
Resetting SMC (Numerous times)
Vacuming the air vents
Reinstalling the system
Also SMCFancontrol won't help as it can't slow down fans only make them go even faster (I definitely don't want that).
There's numerous threads about racing and noisy fans on the boards but none with a definite solution to the problem.
I have been a very happy switcher for more than 2 years now, but with this being the second iMac of mine to show this behavior, I'm starting to losing faith in the iMac cooling fan system.
My first iMac had the exact same problem (Racing CPU Fan) and spent most of its short life in the repairs. Finally after two failed attempts to repair it Apple replaced it with my current model that shows the same annoying behavior.
I'm ready to try creative solutions as this is my last resort and the next step is 'retiring' the iMac. The ideal solution for me would be a way to limit the CPU Fan to the usual 1000 rpms and prevent it from going higher. I am totally willing to risk it.
Any help is much appreciated.
Cheers, Jez.
iMac (Early 2008) Intel Core 2 Duo 2.66 GHz, 4 GB RAM, Mac OS X (10.6.4), Boot Camp Partition with Windows 7, 64 Bit