OK - I have fixed the problem. It does seem to be a Firmware issue**. Specifically some firmware after 2.40.40.40. To recap: System 1 - Fan 4 always on full speed. - 2.63.60.62, bios 2.9 System 2 - Fan 4 always on, very low speed. - 2.65.65.65, bios 2.4   System 2 was originally upgraded from a v1 FW, walking through a few versions including 2.40.40.40 then directly to 2.65.65.65, I wasn't sure but I didn't notice the fan being on low all the time until I updated to 2.65.65.65. That's when I started noticing it. So I rolled it back to 2.40.40.40 - the low speed fan 4 has stopped! Next, as recommended, I updated system 1 (with the full speed fan 4) from 2.63.60.62 to latest 2.65.65.65. No change. So I downgraded system 1 to 2.40.40.40 - this FIXED the fan 4 full speed issue. Both systems are now on 2.40.40.40 and both are operating normally, system off = fans off. IDK exactly which FW causing the issue but it's between 2.40.40.40 and 2.63.60.62.   **(The complication is that System 1 was once running normally with 2.65.65.65 - the high speed fan 4 was an issue that developed after that system had been off for some time)
I have two r720s BOTH have developed an issue where Fan 4 keeps running even when the system is off. One system has iDrac FW 2.65.65.65 and the fan stays on very low speed, the other FW 2.63.60.62 and the fan is always at full blast, system on or off. The second system was purchased in order to fix the issue of the first with a MB swap. But it too developed this problem - on the same fan - after updating the FW to current. I have read 1 other post here with the same problem, their solution being to revert to a much older (v1) FW. The fact I have 2 systems displaying an identical issue on the same fan seems to confirm it is the FW. I realise these are older systems but can anyone at Dell offer some insight regarding which FW is recommended to fix this issue? 2.65.65.65 is the last for the r720 I believe - perhaps there is some other driver or combination of bios & FW that will stop these errant fan 4s? System 1 - FW 2.63.60.62, bios 2.9.0 (Fan 4 full blast at all times) System 2 - FW 2.65.65.65, bios 2.4.3 (Fan 4 on low speed after system is off)
r720 Fan 4 still running after shutdown