papst fan problem
 

i have this papst 4412FGML 120mm fan, when i boot the pc it spins a bit and after 20 secs it stops, when i give it a slight swing it start spinning again for 20 secs or so...

But not reliable to use on the cpu sink...

What might be the problem here?

It's one red and one blue cable, in the middle there's an open spot, there i soldered another cable for rpm like it shows in some howto's, perhaps there went something wrong?

is the fan undervolted? eg on 4V instead of 12V.

no i connected it directly to a 12V molex of the psu

Fan is undervolted.

that seems to be possible

but how? it's connected directly to a molex 12V

how did u connect it?
yellow-black = 12v
red-black = 5v
yellow-red = 7v

you've swapped the 12v cable with the 5v cable? some fans don't work properly at that voltage

it's 12V for sure...
when connected I measured voltage with a multimeter ... it indicated 11.92V...

Disconnect the wire for rpm monitoring. If you still got the same problem, and you're absolutly sure it's 12V... seems like your fan is dead.

Is it a new one? If not, did it used to work fine?

rpm wire wasn't connected ...

when it was connected to mobo to monitor rpm, system wouldn't boot it seemed


but even with wire not connected, fan only spins 30secs max and not even at full speed i think