power supply overheating? bad to run fans high?

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power supply overheating? bad to run fans high?

For awhile i've had a problem where if I burn DVD's (not dual layer) my imac will shut off all of a sudden. No shutdown procedure, just off like unplugging it. This doesn't happen with dual layer dvds or cds usually. It did happen today with a dual layer dvd though. I got a program to monitor temps. and noticed the power supply was reaching 82-85c. That is insanely hot.... the only thing i've ever had get that hot was an alienware laptop I overclocked with special cooling that would heat the bottom of the case to temperatures that would burn skin through pants, lol. BUT, I have not done anything to my imac and don't want to void the warranty. I noticed the Optical drive would reach 48c when burning something and at the same time the power supply goes way up. Just browsing the net the power supply sits in mid 60's c.

Is it bad if I use a program to increase the minimum fan temp. and run them higher? I built a computer a few years ago that sounded like a jet airplane because of all the fans that I had to have maxed out from overclocking it. I don't mind the loud noise so would it be bad to have the fans turned way up when i'm gaming, or working the hardware hard?

Power supply browsing the net - 60-66c
browsing the net and burning a DL DVD - 80+c (85c is the highest i've seen so far)
browsing the net with fans turned up - 46c
browsing the net and burning a DVD with fans turned up - will test after posting this and edit in a few.

iMac 20" 2.4Ghz, Mac OS X (10.4.11)

Posted on Feb 24, 2008 2:13 PM

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Answer 1

xmdsys Author

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Feb 24, 2008 2:52 PM in response to xmdsys

wow, with the fans turned up and burning a dual layer dvd while browsing the net the power supply only hit 48c. Optical drive hit 37c. It was so steady I turned the fans down to about 2500rpm and the power supply only hit 55c, optical drive hit 38c. Thats a huge difference from 85c for the power supply. Now i'm going to try burning a normal dvd and see if it suddenly shuts off.

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Answer 2

xmdsys Author

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Feb 24, 2008 3:33 PM in response to xmdsys

Well, 2 successful DVD+R burns finally. These are the first two successful DVD burns (aside from DL) from my imac. I had the fans running at 2500rpm and the power supply stayed right around 60c. I'd say the 1500rpm fan increase is well worth it to keep the power supply under 60c vs the 85c I was getting. 25c difference!

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Answer 3

Feb 24, 2008 4:54 PM in response to xmdsys

I do believe that increasing your fan speeds to keep your iMac running cooler is a good thing. However since your machine was having shut down issues and is still under warranty, I would not use the fan controls in order to amend the problem. Personally I would back up all of your data set the fan speeds back to normal and if the problem persist call Apple and have it repaired. Because if there is an issue with the power supply it will eventually fail and it'd be preferable to get it repaired sooner than later.

The hottest my power supply ever got with the default fan speeds was 71C and I have the 24". I've currently bumped the fan speeds up only a small amount and all my temps usually stay under 50C.

George

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Answer 4

xmdsys Author

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Feb 24, 2008 10:01 PM in response to George Peters

thanks for the reply. I do agree that if there is an issue I should get it fixed rather than working around it. But I don't actually think there is an issue with the hardware other than the fans not speeding up when they should (which is a personal opinion of when they should vs the apple engineers). The shutdowns were not random and were only happening during a specific event. After watching the power supply reach 85c that was a pretty good indication that the imac was simply protecting itself from heat damage by cutting the power. Many other people are having shutdown issues and I would be willing to bet there isn't a hardware issue at all, apple just simply needs to set the fans to speed up at lower temperatures...but they would rather have an oven that is quiet than a cool operating computer that is just barely louder from higher rpm fans.

You have a larger model so I would bet you're components have more space to "breathe" resulting in lower temps. My fans NEVER kicked up unless I was playing games for hours and even then they barely sped up. It seems that after I bumped up the fans even just 500rpms made a HUGE difference so the hardware doesn't have problems, they just need some fresh air.

Soo.... APPLE PLEASE SET THE FANS TO SPEED UP AT LOWER TEMPERATURES!!! Even just a few hundred rpms to cool down the power supply.

Sorry for the long reply George.... I guess i'm just type happy 🙂

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Answer 5

Feb 25, 2008 3:09 AM in response to xmdsys

First I'd like to say that I very much agree with you on this topic but with some variance. I experienced the same thing with my iMac as the temps went up the fans never increased. Anyway I was not able to find any information regarding the iMac shutting down to protect against over heating. From what I've heard the iMac is supposed to go into a forced sleep mode if it overheats. The only thing I can conclude is that it only applies to the processor, as the processor is the only component which has a said maximum operating temperature. Any other component over heating could have unknown results.

I think it's safer to assume that since Apple engineers designed the iMac to run at certain temperatures, whether you or I agree on those temps or not, that it should at least operate at those temps without failure. Keep in mind defective components are very likely to rise in temp when they go out of spec. For example there are many small components that make up something such as the power supply and when small components fail it could cause the rest of the device to increase in temp as it tries to keep operating. So it's quite difficult to be certain if heat is actually the cause of your problem or just a side effect. If it truly is a heat induced problem then Apple has to pay the price for all the repairs and I hope they eventually figure it out.

As for my iMac compared to your's, the 24" iMac has a 280 watt power supply where the 20" has a 200 watt. The 24" panel draws more power for the back lighting and the 2.8GHz processor could arguably produce more heat. So even though it has a greater lateral surface area, the thickness of the iMac is still the same. And the thickness doesn't really allow for that much more ambient airflow inside.

I don't think there is necessarily anything wrong with the default speeds if only they would increase as they should with temperature. I'm no engineer so I'm just happy to have my fan controller so that I can pretend to be smart.

Payback for the long reply x2 🙂

George

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Answer 6

xmdsys Author

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5 points

Feb 25, 2008 9:43 AM in response to George Peters

I thought power supplies had some sort of temperature protection? Well, the types in laptops. I agree that it should operate without failure and at whatever temperatures Apple designed them to run at but....I think Apple was wrong. They shouldn't have designed the imac to run so hot. I'm betting it was more of a thing like Mr. Jobs told the engineers he didn't want to hear a whisper from it so the engineers did just that....but at the cost of the life and dependability of the hardware.

I don't want to have to get my imac replaced every 6 months because they would rather sell a quiet computer than a cool running one. If one core component goes out on a computer, it stops operating, it doesn't compensate for that broken component. (not quite the case for CPU's or GPU's but thats another story)

I actually went to school for electronics engineering (although I left 1 1/2 years early, I still learned A LOT). So i'm sort of kicking myself for not realizing it was probably a heat issue. I would LOVE to tear into one of these iMacs but I don't want to void any warranties. I disassembled an alienware laptop I had and noticed just how "stock" they did things. I upgraded several cooling components and re-routed the wireless antenna. It made a world of difference in it's temperatures (I ended up overclocking it...and it was a laptop!). So i'm sure these iMacs are capable of better but thats the struggle between engineers and the guys with the money telling them how things should be, lol.

BTW, i'm jealous of your iMac. I wish I could have been able to afford that one. 🙂

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