MP 1,1-5,1 Mac Pro Fan Issue

[Svenisak]

No, I don’t have any issues with fans of the Mac Pro in general. Just one fan in particular. The Expansion Slots fan in my 2010 Mac Pro.

It has used to be that if I shut down the MP for a while (over night say) the fan speeds up to about 2000 rpm, and settled down to a “normal” 600-800 rpm after an (like) hour. This did not happen with with “sleep” or “restart”.

I use the past tense for a reason. Yesterday, I upgraded the processors, and now the fan seems stuck at ≈ 2000 rpm. Note that the Expansion Slots fan has nothing to do with the Processor Tray. I didn’t even touch it (other than clean it, with some compressed air).

This may not seem to be a big deal. But, the added noise level of running the fan at 3 x “normal” speed is quite annoying, as I use the computer in a recording studio.

Any suggestion of a solution to this issue would be appreciated.

 

[rpmurray]

Not that it will particularly tell you the reason for it but you might try one of the fan control apps like Macs Fan Control and see if you can change the speed of the fan just to make sure it's not a hardware issue. Did you do an NVRAM or SMC reset? Making a hardware modification, like changing out the processors, may require a reset of those settings.

 

[chabig]

It could also be that you disconnected something, so the fan runs at full speed by default.

 

[Svenisak]

Did you do an NVRAM or SMC reset?

Not intentionally. I replaced the processors on the tray. Put the tray back and booted the computer. I didn't change any settings. All I did with the Expansion Slots fan was cleaning it with compressed air.

Also note that it did start with the fan att ≈ 2000 rpm before I changed the processor. The only difference is that it spooled back after an hour or so and now it doesn't.

 

[Svenisak]

It could also be that you disconnected something, so the fan runs at full speed by default.

No, I didn't disconnect anything. I didn't even touch the fan (other than clean it by blowing some compressed air on it).

Also note that it did start with the fan att ≈ 2000 rpm before I changed the processor. The only difference is that it spooled back after an hour or so and now it doesn't.

 

[KeesMacPro]

I've got the same phenomenon on one of my MP.
This started after installing another GPU.
But, since i like to set the fans to my taste and workload anyway (MacsFanControl), I only notice it during booting until I log in.


Perhaps it could be the "racing fan bug" , if all Temp sensor readings are still correct (can be seen with e.g.iStatsmeu, MacsFanControl etc).

AirOut: A solution to the racing fan bug

Introduction The racing fan bug is a well known issue that affects certain cMP systems with upgraded video cards, particularly systems with SMC version 1.39f5. On these systems the PCI, PS, and booster fans spin abnormally fast at idle, causing unnecessary noise. Although the issue appears to...

forums.macrumors.com

 

[Svenisak]

This is kinda strange. I didn't make the connection of changing the CPUs with the GPU! Anyway, after having read KeesMacPros post above, I took a chance and launched DaVinci Resolve. Not expecting very much,

I don't know how long it took, but when I looked about 10 minutes later, the fan had spooled down to "normal" rpms. Actually, the Power Supply fan rpms had halved aswell.

 

[KeesMacPro]

This is kinda strange. I didn't make the connection of changing the CPUs with the GPU!

AFAIK it remains unknown why exactly this occurs.
It seems that the power draw from the PCI slots can trigger it, but other hardware may influence it as well...