Precision 5820 - Loud Fans

Hello,

I’m currently having issues with my Dell Precision 5820 workstation where the system fan goes really loud. The fan will start off with low RPMs and once it goes to around 3000 RPM it will hover around there. The motherboard, power supply, and system fan/cpu fans have already been replaced. It is also on the latest BIOS version. I’ve tried changing power plans and changing bios settings to put thermal mode to low without success. Diagnostic test does not come up with any issues either. Changing fan speed in hwinfo64 seemed to have no success either weirdly.

Are there any thermal sensors that could be faulty? Not sure if there are any thermal sensors installed on this PC. 

Please let me know if you have any suggestions.