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Hi all,

Main machine is a cheese grater MacPro 4,1 flashed to 5,1 and upgraded to 8x3.33. I did the upgrade several years ago and everything has been working perfectly since.

....until this morning.

Boot up the machine this morning and, all of a sudden, the fans (booster fans specifically) are running like crazy at 5200+rpm despite both CPUs reading 90-95degrees. I've tried resetting PRAM and SMC but it hasn't made any difference.

I DID notice some weirdness yesterday with the machine while copying a project off to the archive drive. It kept erring out and telling me such-and-such a file had unreadable data. Transferring that file individually worked just fine. Chalked it up to a disk issue and plan to replace that disk this weekend or next week.

In the meantime, the fans have started going crazy and won't stop.

The nation's knowledge runs far deeper than my own. Any suggestions? Help!

I could never resolve the same issue with my iMac.

Its fans sometimes go nuts, out of the blue, even while sleeping, into a fan craze fest.

Sometimes reseting the PRAM or the other setting (forgot its name) work, but usually not.
And this problem seems to be "by seasons". It hasn't done it in a while... No apparent pattern to chase.

Might be a faulty heat sensor.

Most likely cause: The heat sinks on these are known to clog up with dust. Look between the fins.

The NV RAM battery can be too old. 5 years is the normal replacement interval. A bad battery is far worse than no battery. Use the common CR2032.

You could have a bad sensor or other issues but the above are common.

sndmarks wrote:Hi all,

Main machine is a cheese grater MacPro 4,1 flashed to 5,1 and upgraded to 8x3.33. I did the upgrade several years ago and everything has been working perfectly since.

....until this morning.

Boot up the machine this morning and, all of a sudden, the fans (booster fans specifically) are running like crazy at 5200+rpm despite both CPUs reading 90-95degrees. I've tried resetting PRAM and SMC but it hasn't made any difference.

I DID notice some weirdness yesterday with the machine while copying a project off to the archive drive. It kept erring out and telling me such-and-such a file had unreadable data. Transferring that file individually worked just fine. Chalked it up to a disk issue and plan to replace that disk this weekend or next week.

In the meantime, the fans have started going crazy and won't stop.

The nation's knowledge runs far deeper than my own. Any suggestions? Help!

Could be the seating of one of the CPUs.

http://thexlab.com/faqs/resetpmchip.html

https://support.apple.com/en-us/HT201295

If the CPU is properly seated, the heat sink clear and the NV RAM battery not too low.

Been there on an iMac; it was a loose sensor cable on the motherboard that needed to be taped down with some antistatic tape. I tried all of the fan control utilities and none of them worked for me.

cuttime wrote:... I tried all of the fan control utilities and none of them worked for me.

Yes, avoid those. If overheating is the problem, turning the fans down can destroy your Mac.

I second Mike. Clean out the dust. It cured a similar issue for me.


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