Replacing/Fixing BOOST fan in Mac Pro 5,1

[whoisandy]

My BOOSTB fan reads "0" rpm in Macs Fan Control app so I popped the case off and indeed, it is not spinning. BOOSTB is the fan inside the CPU heatsink enclosure for the left CPU. Here's a screen shot after an hour of CPU rendering a 3D project. You can see all CPU B temperatures are hotter than CPU A temps.

I see a lot of information regarding the CPU tray fans - which I believe is intake and exhaust - but I'm not finding a lot of information about the BOOST fans. Any easy troubleshooting tips? I haven't taken out the CPU tray yet to examine. Just wondering if anyone knows any tips or suggestions. Hoping if I have to replace it, I don't have to dissemble the heatsink from the cpu.

Thanks

 

[h9826790]

Something is very wrong. Not just booster B, but also booster A. With that speed, the CPU A should not able to touch 80C no matter how you stress it.

Try manually spin up the intake to 1300RPM, and exhaust to 1200RPM. See if that can keep both CPU below 80C.

Of course, it's much better to fix the booster B fan, but if cannot, try remove it. The fan now at there will create lots of drag and significantly slow down the air flow. Remove it and rely on the intake / exhaust fan should be OK to keep CPU B cool enough until you get the replacement.

N.B. If you ever perform any CPU upgrade. Check the fan connector again.