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iMac fan goes crazy

rogersmj

rogersmj

macrumors 68020
Original poster
Sep 10, 2006
2,169
36
Indianapolis, IN
Three times now, over the last two months (at least three times that I've been around to notice it), my iMac's fan has suddenly spun up from near-silent to full-blast-I'm-about-to-take-off-from-your-desk. It then gradually (VERY gradually) winds down to normal, near-silent speeds again over the course of about a minute and a half.

I've got iStat, and there's only minimal CPU usage and there's no temp spikes when this happens. This time I was just browsing the web; last time it happened, I wasn't even using the computer. Any ideas to fix this? Anyone else have this happen?
 
Same thing happened to me for the first time last night. Incredibly loud and sudden- scared the crap out of me. If it happens again I'll call applecare, please post any other experiences here as well....
 
The first day I got my imac about 12 days ago now after a few hours of use I left my computer. I returned a while later and when I was about to sit down my imac made the noise you are describing it was a loud fan noise. It was crazy loud. I thought it was weird. I have never heard it do that again since though. Not sure what caused it or why it would do that only never to do again but it was weird for sure.
 
Well, thanks for the tip about the SMC reset, but I basically did that when I moved three weeks ago and it's done it once since then.

I don't really care that much I guess, since the thing is dead silent most of the time. Like I said, this has only happened three times in months. As long as it's that rare, I'm not going to bother handing it over to Apple. Maybe a firmware update in the future will fix it.
 
I just had it a couple of minutes ago! Out of nowhere.
And it scared the crap out of me, I thought it was gonna blow up in my face or something:p

Do you also have a 20" iMac intel Core 2 Duo (with upgraded Ram & Graphics card) ?
 
I am having problems as well

I have tried resetting the SMU but I am still having 2 problems on my G5 iMac over the past couple of weeks:

1.when the iMac goes into sleep mode (either because I put it in sleep mode or due to inactiviy) it shuts down after awhile. The power button stops pulsing and the machine is off. I can restart it normally. This happens all the time now.
2. On occasion, after the computer has gone into "sleep mode" the fan gets really loud. Apart from the fan noise, the iMac appears to be off - the power button is off, teh screen is balnk and the computer does not respond. Hitting the power button does absolutely nothing. It doesn't turn the fan off, it doesn't start the computer. I have to turn the power off at the power bar. That stops the fan and allows me to power the computer back up.

I could be wrong, but it seems like I've been having these problems since I downloaded the latest software update.

Advice?
 
Edwin the Elder said:
I have tried resetting the SMU but I am still having 2 problems on my G5 iMac over the past couple of weeks:

1.when the iMac goes into sleep mode (either because I put it in sleep mode or due to inactiviy) it shuts down after awhile. The power button stops pulsing and the machine is off. I can restart it normally. This happens all the time now.
2. On occasion, after the computer has gone into "sleep mode" the fan gets really loud. Apart from the fan noise, the iMac appears to be off - the power button is off, teh screen is balnk and the computer does not respond. Hitting the power button does absolutely nothing. It doesn't turn the fan off, it doesn't start the computer. I have to turn the power off at the power bar. That stops the fan and allows me to power the computer back up.

I could be wrong, but it seems like I've been having these problems since I downloaded the latest software update.

Advice?
Click to expand...
Sorry, can't really help you there. It does sound like it is a problem that really should be adressed. Good luck!

As for the poster, that fan thing is definitely not normal. There was a point where my PC did the same thing for an unknown reason, but I formatted it and it hasnt' done it since. Not sure if that even fixed it....so don't quote me! Good luck to you as well.
 
Oh. I read the thread title and I was imagining someone running around hysterically going "wwaaaaahhhh! I love iMacs!" :p
 
FWIW, it hasn't happened to me since I originally created this thread. I do always stay current with software and firmware updates.

2Shae said:
I just had it a couple of minutes ago! Out of nowhere.
And it scared the crap out of me, I thought it was gonna blow up in my face or something:p

Do you also have a 20" iMac intel Core 2 Duo (with upgraded Ram & Graphics card) ?
Click to expand...

I have that iMac (see sig), but not the upgraded graphics.
 
iMac fan goes crazy

mrogers said:
Three times now, over the last two months (at least three times that I've been around to notice it), my iMac's fan has suddenly spun up from near-silent to full-blast-I'm-about-to-take-off-from-your-desk. It then gradually (VERY gradually) winds down to normal, near-silent speeds again over the course of about a minute and a half.
Click to expand...

The flat panel iMacs just prior to the intel iMacs had a similar problems which turned out to be a Power Supply problem. My sister had to have the power supply replaced along with the motherboard. It worked great after that, but it was a struggle to get the problem diagnosed. The first sign though was the fan would seemingly spin out of control. Good luck!
 
mainemacuser said:
The flat panel iMacs just prior to the intel iMacs had a similar problems which turned out to be a Power Supply problem. My sister had to have the power supply replaced along with the motherboard. It worked great after that, but it was a struggle to get the problem diagnosed. The first sign though was the fan would seemingly spin out of control. Good luck!
Click to expand...
Most interesting. Thanks!
 
2Shae said:
Do you also have a 20" iMac intel Core 2 Duo (with upgraded Ram & Graphics card) ?
Click to expand...

My iMac G5 with isight does that every so often. It maybe happened 10 times in last 16 months or so. I also have no idea what is that. I remeber calling apple about that but they weren't any help, and cos this iMac is at my gf house in Poland I just asummed that as long as works Im not gonna be shipping it back to US just to take it to aplle store. Especially that its really rare...
 
Well this thread is more bustling than mine so-

I had this happen to me last night. I've spent more time under XP since Christmas (big uni project, PC app only etc) and it happened in the short window that I used OSX for last night. Latest f/w and everything. Not hot, no huge applications running...
The mystery continues.
 
resetting the SMC worked for me

iMAC 7.1 with Intel core duo SMC version 21f4
went crazy with fan spinning like a windmill after just standard power on.
No improvement after multiple shutdown and restart. :eek:

I was able to fix it thanks to VanNess and his link

I suspect this is related to my recent practice of turning off power at night to the power string where my iMAC and other peripherals are attached. :confused:

I understand now this practice is equivalent to reset SMC every night.
 
i've had this happen twice on my white imac 2.16ghz.

i think it might have something to do with java.
 
hahaha im just picturin someone sitting there and then they hear some loud random noise, the reaction hahah
 
Mr Skills said:
Oh. I read the thread title and I was imagining someone running around hysterically going "wwaaaaahhhh! I love iMacs!" :p
Click to expand...

Ahha! You just made my day!!!

My iMac has done this maybe 5 times in the last 3 days, I don't know what I'm supposed to do, its driving me crazy
 
I had an I7 that sped up from silence to a "wind turbine" noise with zero programs running, and nothing taxing the CPU. It took around 30 minutes and gradually kicked in.

I replaced the set up with an I5 plus a "regular" 27" iMac combo (dual monitors), and both are completely silent, no matter what I throw at them. I can literally hear road noise outside my double-glazed windows -- there's nothing to suggest the Macs are on except for the screens!

My (completely amateur) advice? I was told the "fan noise" issue was a sensor problem. But that's MY distinct issue rather than the fan suddenly roaring. I installed istat to check RPMs, and my CPU fan was rocking at 6500+ (apparently normal operating levels are around 1000).

Get the unit replaced or repaired if you can't live with the noise, I reckon.
 
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