AX850 PSU Fan Operation Query

Hi,

I've had a AX850 PSU for about 2 years, up until now the PSU has been mounted in a Corsair Graphite 600t case with the fan located at the bottom. I just recently bought a new Fractal Design Define R4 case and when exchanging components between cases I noticed that the PSU fan is clean as a whistle with not a single spot of dust on it. You would think after two years there would be some dust build up but this PSU looks brand new. This makes me wonder if the fan has ever worked as intended.

So I installed the PSU into the new case with the fan on the top so that I could monitor if it worked or not. What I've noticed may be by design but I need confirmation.

Observations:

1. When I turn the PC on the PSU fan spins up briefly then stops.
   
2. Every 2 mins or so the PSU fan spins up for about 15 seconds then stops.
   
3. When the fan does spin up its RPM appears to be incredibly low so the effectiveness of thermal reduction is questionable.
   

Questions:

1. Is this by design?
   
2. Shouldn't there be at least *some* airflow over the internal PSU components even during times of idle? If not this sounds like a terrible thermal design flaw.
   

Note that up until now I have been under the impression that the PSU has worked correctly and as intended and only through these observations have I started to question the integrity of the components.

I am unable to ascertain if this occurs more frequently during times of increased load as the fan seems to turn on fairly randomly.

I'm looking to buy one of these kits but before I do I need to know if this PSU is okay, otherwise I won't throw more money at it and would rather get it replaced / buy a new one.

What is the part number on the PSU? If it is CMPSU-850AX It's one of the newer models that are are fanless at low loads/temps. and from what you describe sounds like you have one of the newer ones.

Are you experiencing any stability issues that would tend to think your PSU is faulty, or just lack of dust build up?

Questions:

 

Is this by design?

Shouldn't there be at least *some* airflow over the internal PSU components even during times of idle? If not this sounds like a terrible thermal design flaw.

1)Yes, it's by design if it is a newer model, but ,

2)No Not really, it's all about efficiency. At low loads they do not produce heat like PSU's of days gone by. No need for the extra airflow at idle conditions. Go ahead and buy your cables if the part number matches the one I provided! :)

What is the part number on the PSU? If it is CMPSU-850AX It's one of the newer models that are are fanless at low loads/temps. and from what you describe sounds like you have one of the newer ones.

 

Are you experiencing any stability issues that would tend to think your PSU is faulty, or just lack of dust build up?

The part number matches! I did observe that while running Prime95 the PSU fan spins up almost immediately and continues to run until I close Prime95. So it appears to be working!

This has given me more assurance and I'm glad I don't need to pony up another $200 :)

I'm not experiencing any stability issues whatsoever. Looks like I can take a deep breath. Thanks for the input.