2011 21.5 INCH IMAC i5 500GB Fans on Constatly


macrumors newbie
Original poster
Mar 11, 2012
Hi new to the forum and just wanted to see everyone's opinion on my macs fan problem

its the 21.5 inch imac i5 and less than a month old now i didn't notice it when i first powered it up but you can hear the fans whurrring away even with nothing running, i have tried the smc reset but didn't help also tried the pram reset but every time i try it it boots up as if you just bought it asking to use a time machine to restore the os, i did the pram reset on my 2011 macbook pro and beeped restarted and worked fine,

using istat nano i got these fan speed reading

Optical drive 3498rpm
Hard drive 3500rpm
CPU fan 1198rpm

also here are the temps

HD 32
CPU A 35

can anyone have a look at these figures and see if the normal
all help would be very much appreciated


macrumors Westmere
May 16, 2008
The Intel processors used in Macs are designed to automatically shut down to prevent damage if they truly overheat. CPU Tjmax = 105C, GPU Tjmax = 100C on i3, i5, i7 processors. (Source: Intel) If you're not already using it, iStat Pro will give you accurate readings of your temps and fan speeds, among other things.

Unless there is a rare defect in a Mac, most temps are well within the normal operating range, considering the workload being put on it. Websites with Flash content, games and other multimedia apps will put higher demand on the CPU/GPU, generating more heat. This is normal. If you're constantly putting high demands on your system, such as gaming or other multimedia tasks, expect temps to rise and fans to spin up accordingly. It's just your Mac doing its job to maintain temps within the normal range.

It is also quite normal for your Mac to become extremely hot to the touch during intensive operations. The aluminum body transfers heat more effectively than other materials used in computer casings, so you will feel the heat more. This doesn't indicate that it's overheating and will not harm the computer to be hot to the touch.

Your fans are always on when your Mac is on, spinning at a minimum of 2000 rpm (for MBPs) or 1800 rpm (for MBAs, MBs and minis). iMacs have 3 fans with minimum speeds in the 800-1200 range. They will spin faster as needed to keep temps at a safe level. If they're spinning up without increased heat, try resetting the SMC. (PRAM/NVRAM has nothing to do with these issues, so resetting it will not help.)

The intake and exhaust vents are in the back of the computer near the hinge on all Mac notebooks. The iMac vent is a slot on the back near the top of the computer. Make sure the vents remain unblocked to allow your computer to perform at its best.

Learn about the fans in your Mac
Apple Portables: Operating temperature

For Flash-related issues:
Launch Activity Monitor and change "My Processes" at the top to "All Processes", then click on the CPU column heading once or twice, so the arrow points downward (highest values on top). Then look to see what may be consuming system resources.

If a drive is constantly active or your CPU utilization is high (possibly with increased temps and fan speed) when you're not running any major apps, check to see if Spotlight is indexing by looking at the Menu Bar icon:
(not indexing)
(indexing) (pulsing dot)​


macrumors newbie
Original poster
Mar 11, 2012
tried the smc reset did not work my fans seem to be running to high at normal operating temps