CPU Fan: Idle at 1k RPM, Is This Normal? (Very loud)

[greenfrog5]

I recently upgraded my Chimera/Yosemite hackintosh to a clean-install of Mojave, with Clover. I also changed out my GPU for RX 560 because my old Radeon is no longer compatible. At first, I though the RX 560 fan was the problem, as this seemed to be the main "change." Once I finally got my sensors working with HWMonitor, I believe the GPU fan is generally not spinning (which it shouldn't be on minimal use), and my CPU fan spins at 1k+ at all times. At the moment, my CPU cores are 37-40 C, and the CPU fan is spinning at 1080 rpm, and making a lot of noise. I recently booted up, and have 4 tabs open in Firefox (and nothing else running).

Many times, the fan spins up to this noise level (estimated 1k rpm) as soon as the machine is turned on, and over the next several hours gets louder and louder. I have tried resetting SMC, PRAM, resetting BIOS. From what I have gathered, the OS does not do much with the fan speeds, and it is not likely a kext issue. I have read it could be a power management issue, but I'm not sure how to diagnose that (I've tried NullCPUPower, and some other power-related tweaks). Resetting the SMC (unplugging for a while), then boot Clover, then F11 to reset PRAM, then boot up system, the fan starts a bit quieter, but eventually moves up to 1k, without even doing anything on the computer (even just leaving at login screen).

Is 1k rpm at 40 C (with no load) normal? As I've been chasing my tail searching for GPU fan issues, I am only now starting to monitor the CPU fan behavior in more detail, and and am suspecting there might be something wrong with the fan itself? If 1k rpm is normal, but shouldn't be this loud. When I updated my system, I did open the case and blow all the dust out, being careful to hold the fans so they didn't spin up too much with the compressed air, and then replace my GPU. It is possible I dislodged the fan from the heat sync, that dust got blown into something, or that I otherwise damaged the fan, knocked it out of alignment, etc. I think I have another (new) fan I can try, not sure if it is the right size/type, but thought some of you folks might be able to help me avoid an unnecessary fan swap...

Hoping for a second opinion on whether it "sounds" like I have a hardware problem, or what other steps I should try to troubleshoot. How slow should I expect the CPU fan to get when the computer is running, but doing nothing? Should 1k rpm create a steady buzzing noise? I see my fan maxes out at 6k rpm, so I'm beginning to suspect 1k is normal, but shouldn't be this loud (i.e. bad fan). I never needed to pay attention to this before, so I don't have a good frame of reference (no idea how it performed on my old system, because it was never loud enough to notice). I remember my old system running very quite, and fans ramping up when use/load increased, as expected.

 

[greenfrog5]

As I continue to investigate this, it seems like both my CPU and case fans (and possibly the GPU fan) are all contributing to increased/excessive noise (compared to my old system). I was able to get my fan sensors working briefly, but in troubleshooting other Clover/boot issues, I have broken that and cannot get them to show up in HWSensors again...

Is there anything I can try, or check to help diagnose this problem?

 

[greenfrog5]

I have got my FakeSMC sensors working and my CPU fan runs around 900-1100, and the System Fan runs around 200-500. I have also installed Macs Fan Control, which does seem to work in controlling my fans. However, for my System Fan, it gives an error "Something is wrong - min/max fan values are equal (65535). Please make sure to uninstall any other fan controlling software and reset SMC". The System Fan is running around 220.

I have disabled HWMonitors, and don't have any other fan software. What does this error mean, and how can I fix the cause? There is no SMC to reset on my hack, right?

 

[antieatingactivist]

The OS has nothing to do with your CPU fan speed. Its possible to enable control through macOS, but if you haven't set that up, its not happening. I Checked out the manual for your motherboard. 1st, make sure your CPU fan is plugged into the only 4 pin fan header, not the 3 pin. (im assuming your cpu fan is 4 pin). if you've verified this, you have a setting in your bios called CPU smart fan control. If its running too fast for your liking, change this to a different setting. The motherboard directly regulated the fan speed against the temperature of the CPU unless the OS intervenes. You can use HWMonitor without trouble.

 

[greenfrog5]

Thanks. System and CPU fans are installed correctly. While investigating this I realized I have another lower-front intake fan and saw that it was plugged into an adapter and directly into my power supply. The cable didn't reach,a nd I didn't really know better at the time. Oops! This has been this way for 10 years, I guess running full all the time. Although this fan full-on is not actually that loud, disconnecting it caused the other system fan to spit a bit faster (and actually sounded quieter/smoother). I then got a fan extension cord and connected what is now System Fan 2 correctly to the motherboard, which shows in HWSensors. Fans tend to run:
CPU: 800 - 1000 rpm
Both system fans: 400-700 rpm

Still seems louder than I recall, but certainly an improvement and seemingly "functioning correctly." The BIOS settings don't have a significant effect on the speeds/noise. I am also curious whether the fans make less noise when spinning a little faster (and maybe they need to be a bit faster, rather than slower). Are the speeds I posted above typical for running very little load?

 

[greenfrog5]

It turns out the most offensive fan noise was the result of a case exhaust fan that was slowly dying. Eventually it got so bad that it was spinning around 100 rpm, and the motor would pulse to try to spin it up, then stop. The other case fan and CPU fan were at 700-1200. Opening the case I could see the bad fan barely spinning. Touching it (to stop it) causes the noise to completely stop. I replace the fan with a spare I had, and it now runs "normally." I have also discovered I likely have some power management issues to work out (CPU idles at high P-state).

 

[RicardoF1RST]

I was just about to suggest that. Circa 1000rpm is basic tickover / normal operation. Normal PC fans run up to 5000rpm when things get warm, more likely a bearing issue as you discovered. Glad its sorted.