Now that the weather is heating up again, and because i don't have aircon where i live, i have noticed that after using my mac (27in screen) for a while i can hear the fan doing its work in the background. Normally it never makes a noise. Additionally the top of the screen is particularly hot, although not so hot i can't put my hand on it.

Clearly the level of external heat determines this happening. I'm not using that many programs, perhaps typing up a document with my internet connection open too, maybe listening to some music.

Is this normal stuff for an imac? Do i need to basically stop using my computer to let it cool down each time? What do other users experience?

I found that only an anti-virus program would get the various Mac-models (MacBook, Macbook Pro, iMac 21 inch, iMac 27 inch) to run warm and for it to get noisy because of the fans working overtime. The minute I quit the anti-virus program, the fans slowed down and the heat disappeared.

Download iStat Pro for Dashboard which shows the temperatures generated and the processes active. That's how I found the culprit.

Thanks for the reply. Can i verify what i've understood?

When you operate your computer without the anti-virus program, it cools down and the fans slow down (can no longer be heard?)?

And that it gets noisy because of your anti-virus program running?

I don't have any anti-virus program (that i know of anyway). I would say i can just sort of hear the fans working in the background, not noisy at all, just sort of audible. The top of my screen feels rather hot, the bottom much less so.

I had read about this istat pro before, but never keen on downloading something unless it get recommended by someone. I guess i should do that.

Right and right.

Thanks for the reply. Can i verify what i've understood?

When you operate your computer without the anti-virus program, it cools down and the fans slow down (can no longer be heard?)?

And that it gets noisy because of your anti-virus program running?

.... I just received my 2nd replacement mac. Yep, 3rd mac in 2 years. Took some complaining to get this one. First issue was an overheat ... shut the lid one day, to take it out of my bag a few hours later, nearly dropped the thing it was that hot.

I had previously told mac care it runs hot ... the guy said "yeah they do run hot, and probably too hot to use on your lap" ... To which I said "Its a bloody laptop!!"