Very High Temperatures with my iMac

80ºC is the temperature I use to determine if temperature is dangerous.

Fans should be turned on automatically to decrease temperature, and you should hear them. If not, reset the SMC > http://support.apple.com/kb/HT3964

Another thing you can do is to increase the fan speed by using smcFanControl. You shouldn't set a fan speed higher than 2000 rpm, which may cause damages.

Finally, to discard a fan problem, use Apple Hardware Test by holding Option (Alt) and D keys while your Mac is starting. Disconnect all peripherals, select the language, mark the box to run an extended test and start the test. If at the end of the test you see an error, copy it here. If you don't get anything, run it again, and if you don't get anything again, your iMac is working correctly

80ºC is the temperature I use to determine if temperature is dangerous.

mende, I've already said this is dangerous advice, especially since you don't say for what hardware component the limit of 80C refers to. I might add that it's a very high limit for almost any component, the PSU included, but running the drive at 80C will doubtless cause the early death of any drive. Even the GPU, which normally can take quite high tempertures, might be adversely affected running long term at 80C.

I don't understand why you insist on repeating this absolutely incorrect and harmful advice and you really should stop.

Another thing you can do is to increase the fan speed by using smcFanControl. Youshouldn't set a fan speed higher than 2000 rpm, which may cause damages.

NO, running the fans through smcFan at 2k rpm long term will prematurely burn up the fan motors. Depending on the Mac and the default idle fan speed, I wouldn't advise going much higher than mid-1600 rpm, at least not for extended periods of time.

WZZZ, for your information, all portable Macs have their fans set at 2000 rpm by default and they do not fail, so maybe you are wrong.

2000 rpm is not a dangerous speed (anything higher would be), as other users state, but 80ºC is a dangerous temperature. I don't know where you got that 2000 rpm damages Macs

WZZZ, for your information, all portable Macs have their fans set at 2000 rpm by default and they do not fail, so maybe you are wrong.

The OP is running an iMac, not a portable.

2000 rpm is not a dangerous speed (anything higher would be), as other users state, but 80ºC is a dangerous temperature. I don't know where you got that 2000 rpm damages Macs

You have been saying that anything up to 80C is acceptable. So you are saying then that a drive running at 75C is OK? See http://www.codinghorror.com/blog/2006/12/hard-drive-temperatures-be-afraid.html It's from some years ago, but no less relevant now. And anyway it makes no sense to talk about one upper limit for all hardware components.

The default idle speeds on my 21.5 are ODD 1000, HDD 1100, and CPU 1200. Running all the fans at 2k long term is a huge jump from there. Not only is it likely to prematurely ruin the fan motors, but at that speed it will suck in an unacceptable amount of dust, causing a vicious circle of overheating from accumulated dust on the hardware and the fan blades, requiring even more cooling.

EDIT: Apples and oranges. The much smaller fan blades on a portable need to spin proportionally faster to achieve the same cooling.

Message was edited by: WZZZ

The fan speed range (on a 13" MBP) is from 2000 (idle) to 6000 (max)

mende1 wrote:

2000 rpm is not a dangerous speed (anything higher would be)

That is just BS, 2000rpm is the fan minimum speed, they run just fine when revolving faster than that.

When my MBP is working hard this is a regular speed: (Temps are in C)

Just let the Mac take care of itself.

WZZZ, thank you for your explaination. Now, let's the OP follow the other steps I gave him/her because they are valid. Again, I don't remember anyone saying that 2000 rpm speeds damaged their Macs, but there are better steps to follow. The SMC reset and Apple Hardware Test should tell us more about the problem.

Csound, I knew that. The worrying problem here is that if we let the Mac take care of itself and fans are not turning on (Apple Hardware Test should reveal it), this will be even worse.

chris_gmu wrote:

i have a 27 inch iMac and the last few days is getting really really hot. I installed temperature monitor and I saw a temperature of 80 degrees of celsious!!

Is it possible to be a software related problem ? Or a hardware ? Any suggestions on how to solve this ?

There are numerous temperature sensors on your Mac. It all depends for just what you saw a temperature of 80C. Can you please post all the temps in Celsius. No one can evaluate what's happening from just one temperature, and especially not knowing what it's for.

Get free Temperature Monitor. Oh I see, you already have that.

http://www.bresink.com/osx/TemperatureMonitor.html

I don't see anything wrong here, 80C is not dangerous (the MBP I referred to is always between 70 and 90C, and has been for the last 4 years)

To say that 'Anything faster than 2000 rpm is dangerous' is a fantasy, regardless of model.

I don't remember anyone saying that 2000 rpm speeds damaged their Macs,

Probably because few use smcFan Control and fewer run the fans that fast constantly. And also because this is something to be concerned about long term, it may be a few years out before the damage to the fan motors becomes noticeable.

We are still talking apples and oranges, MBP/IMac. This thread is getting all bollixed up with that false comparison. Again, the OP in this thread is running an iMac. And I don't understand why you are talking about 80C, as if it's only one temperature. Your drive is running at a nice, relatively cool 43C.

And, as I already said, the fan, or fans, in the portable being small need to run that much faster. The default fan speeds on a 27" iMac (not talking about the newest with only one fan--no idea what the default idle is for that) are even slower than my 21.5.

WZZZ wrote:

We are still talking apples and oranges, MBP/IMac. Again, the OP in this thread is running an iMac. And I don't understand why you are talking about 80C, as if it's only one temperature. Your drive is running at a nice, relatively cool 43C. And, as I already said, the fan, or fans, in the portable being small need to run that much faster. The default fan speeds on a 27" iMac (not talking about the newest) are even slower than my 21.5.

I know that, and I also know the OP has yet to identify which sensor he is referring to. I have a 21.5" 2011 and still don't think that 80C is 'dangerous'

But rather than play this out with you I'll just hand the thread over, knock yourself out.

Knocking myself out.

I wouldn't call anything there critical, but I'd want to see the temps come down a fair bit. And I agree the secondary heatsink is rather high. These are mine, with the fans ramped up using smcFanControl and a fan running at the back.

But how hot is the room you are in? That will have a lot to do with it.

See my posts on using smcFan, in these two threads.

https://discussions.apple.com/thread/3617828?start=0&tstart=0

https://discussions.apple.com/thread/3219643?start=0&tstart=0