Question The fans of the CPU are turning on without connecting the f panel

[DozentM]

I building my third pc rn with:
Gigabyte B550 k m
Ryzen 5 5700G
NM620 Lexar 2TB NVME SSD
G.Skill 32tb RAM
BeQuiet SFX L Power 500
And the Inter-Tech IM-1 Pocket case.
I built it as always making sure everything is connected the right way, but after turning on the PSU the CPU fan(the only one atm) turned on without pressing the power button and my Monitor doesn't receive a signal(tried with HDMi and DP). I tried another ram, but it didn't make a difference. As well as another PSU the Pure Power 10 700w I use in my own build, but still same result (fans turn but no signal). After that disconnected the f panel completely and the fans still turned on, without a signal. Any idea what's happening?

 

[DFace1_2]

Do other fans power on? Does the motherboard power on?
If you power everything down, take the CPU cooler off, clean the CPU but leave it in the socket, reconnect the PSU and switch it on, does the CPU get hot to touch?

If the CPU does get hot, that would indicate the problem could be to do with the PSU.

If it doesn't get hot, there is probably a problem with something between the PSU and the fan connector.

 

[DozentM]

Do other fans power on?

I only have the CPU and PSU fan, so idk unfortunately.

Does the motherboard power on?

It has no LED lights to check this, but a little speaker that makes no noises at all

If you power everything down, take the CPU cooler off, clean the CPU but leave it in the socket, reconnect the PSU and switch it on, does the CPU get hot to touch?

If the CPU does get hot, that would indicate the problem could be to do with the PSU.

If it doesn't get hot, there is probably a problem with something between the PSU and the fan connecto

I haven't tried that yet, but will soon. But in my mind it can't be the PSU, because I tried it with another that has worked for 5 years now. Thus I think its the Mainboard or CPU?!

 

[Zerk2012]

turned on without pressing the power button

Sounds like something is shorted.
Try it with the motherboard out of the case.