Asus B450M-A strange issue. (Solved sort of)

[ShrimpBrime]

Hi all. Came across something that had me stumped for an couple hours.

My office PC I have been using lately though would be a good idea to run passively.
The cpu is a 220ge Athlon, board is B450M-A.

Issue is, unplug the cpu fan from the header, get a notification there's no fan.
I set the setting to ignore in bios and carry on about my business.
Also have the side panel removed which also the fan is plugged into the main board.

Once in windows, maybe 10-20 seconds the system restarts.
When in safe mode, no problems at all. Can run no fans.
Ok reinstalled windows 10. Issue persisted. 

WTF?
Plug the cpu fan back in, now will run 5 minutes and then restart.
Plug the case fan and cpu fan back in, no issues either.

So right no passively cooled, populating the headers seems to work just dandy.

So I've resolved the issue where the system doesnt just restart randomly, but why from these 2 fan headers. 
I cant figure out if it's the board restarting or windows. There's no log file or error even after a windows reset. 

Strange !! 

[Mr.Scott]

If there's no log file, it's a hardware issue, not Windows.

[ShrimpBrime]

Sept 7, 2020 12:17:05 GMT -5 Mr.Scott said:

If there's no log file, it's a hardware issue, not Windows.

After some days of testing with the fans plugged in, I decided to unplug the Cpu fan.
Enter bios and ignore the warning. Does fine, post windows.
Maybe 30 seconds in, restarts no warning.

Plug the cpu fan back in.... work like a charm. Lol. Stupid quirk, but I'll take that over some others that could be.

So far so good. Thirty Eight and one quarter multiplier and been stable for a couple days. 
Tad v-droop at idle 1.384v should be running 1.40v LLC at high setting.

Sturdy though, it's been in operation since 2017 and has seen minor sub zero temps (probably what the quirk is about lol)