Here’s how you can manually control the fan speed on your Poweredge R320/420/620 from the ESXI CLI.
1. Download the ipmitools file which is compatible for ESXI up to 6.7 and upload it to your host. (credits to fatty lewis)
File: IPMITOOLS
or
https://mega.nz/#!U1R2lCpA!eq54PJSw3ErRVTeoPtebLvR6uBJHeZYDuEurPU4tDLI
2. Upload it to your host via WINSCP or SCP CLI
scp ipmitools root@x.x.x.x:/
3. SSH into your host
root@x.x.x.x
4. Make the file executable
chmod +x ipmitools
5. Enable manual fan control
./ipmitool raw 0x30 0x30 0x01 0x00
6. Set fan speed to desired values below
Set fan speed 20%
./ipmitool raw 0x30 0x30 0x02 0xff 0x14
Set fan speed 25%
./ipmitool raw 0x30 0x30 0x02 0xff 0x19
Set fan speed 30%
./ipmitool raw 0x30 0x30 0x02 0xff 0x1e
These commands are not persistent across a reboot.