Fan turning on to 100% after restarting PC

[ChennyBoi]

One of my fans are turning on to 100% RPMs after I restart my computer. Either through windows or I do it manually.
After I shut off my computer and turn it back on, it resets to normal. The fan in question is plugged into SYS_FAN1 and is a 3-pin. I believe it could be something with the motherboard. The fan that goes to 100% is the stock fan that came with the case(Corsair 270R windowless). Temps are the same. I would like to see if there is another problem before I go to send this back in because if I can't get the warranty on it because I did something wrong or set something differently, then I don't want to waste my time, because I'll have to take everything out and send the motherboard alone.

I've tried resetting BIOS and CMOS(Through the pin reset).

Should I send the motherboard back in for the RMA? I have a 30 day limited warranty on it.

I have a Z370 Gaming wifi motherboard - https://www.memoryexpress.com/Products/MX69227

 

[Paul NZ]

Replace it with a 4 pin fan, if the header is 4 pin

 

[ChennyBoi]

Replace it with a 4 pin fan, if the header is 4 pin

I plugged in a 4 pin fan to it, and it functioned as normal. I also plugged the 3 pin fan to another fan header and it would start in 100% rpm without having the pc being restarted? I will probably just buy another fan, but is there any reason why the 3 pin fan when connected to the old header would start normally, but then when it is restart it would go to 100%? This part doesn't make sense to me.

 

[Paul NZ]

Well normally 3 pin fans do run at 100% all the time. With 4 pin they support PWM which can be controlled

I've got 5 3 pins (which had 3 pin and molex - I cut the molex connectors off - I hate them)!, in the other desktop here. 4 pin are just too expensive for 1 here.

I just changed all the fans to PWM in the BIOS lol.

 

[ChennyBoi]

Well normally 3 pin fans do run at 100% all the time. With 4 pin they support PWM which can be controlled

I've got 5 3 pins (which had 3 pin and molex - I cut the molex connectors off - I hate them)!, in the other desktop here. 4 pin are just too expensive for 1 here.

I just changed all the fans to PWM in the BIOS lol.

So I dont understand why restarting my PC triggers it to go to 100%. And then shutting it down and turning it back on sets it back to normal. I checked the bios and tried to set it to PWM, but it just ends up setting it to 100%.