Any PSU fan runs at 100% on ASUS Mobo

[strider21]

Hello,
System config: Intel C2Q 8400; ASUS P5Q PRO; 8GB OCZ 800Mhz
In use from 2010 without any issue
Cleaned the system last week; Now a weird problem: Regardless of which PSU i connect (Corsair CX550/ VS450) 10 minutes after bootup, the psu fans reach 100% speed with full noise. All case fans/ cpu fan/ gnu fan run at normal speed on load/ without load.

• 
  The air blown-out from the PSU fan is cool (while it's running at high speeds) and the surface of the PSU is also cool/ lukewarm to touch.

• 
  When the system is shutdown (but not powered off), the PSU fan spins for about 10 minutes. All the case-fans, cpu heatsink fans are off.

Any suggestions as to what exactly is causing this issue? I suspect the motherboard but can't pinpoint the exact cause.
Thank you.

 

[popatim]

PSU fans, with a few exceptions, control themselves and are not controllable by the user. Keep in mind that probably 90% of psu fans have no control what-so-ever and always run at 100%, while the rest have internal thermistors or dedicated logic to control the fan.


Now there is the possibility that you blew out the psu and over-rev'd its fan which would now make more than normal noise....

 

[strider21]

The PSU works fine if i connect a different motherboard+cpu+ram (set)
With any PSU connected to the P5Q-PRO (cpu+ram), the PSU starts the noise (of fan spinning at 100%)

 

[popatim]

perhaps something about your case/build makes more heat or has less airflow causing the psu's fan to ramp up.
The only fans the motherbd can control are the ones connected to it. CPU & case fans (and case fans are a maybe on the control part of it).

I would be more inclined to believe that its the cpu or gpu fan that you are hearing.