[SOLVED] what can make case fan to spin without being plugged in? since my spinned

FullTank

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Apr 7, 2015
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so funny story happened, my noctua rear case fan spinned without being connected, how exactly it happened i have no idea, any geeks here in that matter? will explain what i done exactly which caused it to spin, step by step

basically i use dual PSU cable which going towards 1200W seasonic 80+ platinum & 1000W evga 80+ gold , my metal case is lying on the carpet floor, my noctua rear fan always was unplugged but screwed in to the rear because i'm waiting for the extensions so that i can plug it, it's connector before such behavior was nearby the top side of the x399 gigabyte designare ex motherboard's heatsink and lying on the metal case, however that's not the cause of such behavior, at least not alone, i'll explain why now

it always was there and never spinned, i had 4 gpus running in CFX , then decided to give a try to 5 gpus, booted, just to find out that 5 gpus cfx is not supported, at this time i also was on my 2nd bios because 1st one once failed to load with some ram sticks which could not handle my desired OC (took them out a bit later but bios remained on 2nd one), i was on 19.12.1 amd drivers and decided to give a go to latest ones just to see if it will somehow work with 5 gpus or no (since no cfx for 5+ gpus apparently even since 2015 and probably even before that)
, opened installer, picked factory reset and right after shutdown the pc just spin all the fans at it's max, including the not plugged in noctua fan even

weird i thought, a bit scary even, with not much of tries, i unplugged 5th gpu, same behavior, weird i thought once again, unplugged another 3 gpus and only 1 remaining, then i also placed the noctua rear fan connector facing the air aka away from the metal case and heatsink - tried to boot, behavior was still same and noctua fan still somehow magically spinned, here's photo of the connector's position but i took it during powered off PC, since i'm not exactly into potential damage https://puu.sh/F2ewh.png , another thing to mention is that during all these booting tries, i was able to turn ON the PC with Power ON button, but was unable to turn it OFF by holding it, was able to turn it OFF only by turning off the main PSU button, and it still was active for around 2-3 seconds even after i turned off the main psu button.

well then, only one thing left, i unplugged the dual psu cable, plugged in just stock seasonic 1200w platinum cable and kept that single GPU , and it booted this time, but noctua unplugged fan still spinned like crazy, but only for around 3-4 seconds and then it stopped and never spinned again, another thing to mention is that it booted on the main bios instead of secondary

and that after that i tested that exact same dual psu cable which i counted as "dead" already, and surprisingly it works just fine in all the stresstests, i gave it another go just because the spare one which i had, brand new, happened to be less strong, could not handle stable power delivery if any of the 4 gpus is on OC, while this one which i counted as "dead" after that story, can handle all 4 gpus on OC , and that story only happened when i gave a go to 5 gpus

whatever that weird thing was, i clearly learned that dual psu cables all are different and have limited stable watts supply, but i just can't get one thing, how exactly did that noctua spinned on it's max RPM or even above that(even when it's connector faced the air), without being plugged in, any geeks are welcomed.. :)
 
Solution
figured it out, apparently my fans are just way too strong, it was just a simple pressure of the 2 CPU cooler fans, since they both are 3000RPM each