Thanks for the hint guys 
bcs I was looking at this no name fan with a 60 day warranty from seller:
http://www.ebay.com/itm/231569988051?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
and by the way, did you bought your fans on ebay/amazon/etc.? or is there someone from bct selling them for BTC?
This is very true here is the official options: https://bitmain.zendesk.com/hc/en-us/articles/204199879-Antminer-S4-fan-specification-and-possible-replacement-fans
Do not just throw a cheap fan in there. There is a BIG difference between a high rpm fan and a cheap fan. With your miner you don't want to use cheap fan and let it get to hot.
I went with sanyo as it has such a high RPM i was impressed. Delta is the more popular option though. Either one listed on the link above is fine.
bcs I was looking at this no name fan with a 60 day warranty from seller:http://www.ebay.com/itm/231569988051?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
and by the way, did you bought your fans on ebay/amazon/etc.? or is there someone from bct selling them for BTC?
you have to find a fan that has a high rpm
This is very true here is the official options: https://bitmain.zendesk.com/hc/en-us/articles/204199879-Antminer-S4-fan-specification-and-possible-replacement-fans
Do not just throw a cheap fan in there. There is a BIG difference between a high rpm fan and a cheap fan. With your miner you don't want to use cheap fan and let it get to hot.
I went with sanyo as it has such a high RPM i was impressed. Delta is the more popular option though. Either one listed on the link above is fine.
Personally I went with amazon as I needed it quick and got 2 day shipping on it through amazon prime. Ebay if those work as promised is not bad. But I personally would get an actual Delta or Sanyo.
The way I see it is why risk a miner for a few bucks on generic fan. That is unless it's very old miner and you don't really care. But S4 still has some value.
You are absolutely right about the quality level.
There is a quote about it: I am not so rich to buy cheap things)
Of course cheaper fans will go out of service faster..actually its a lottery with the brand fans too, but chances are higher)
I downclocked the s4 for stable temps and searching for some eu-based seller to have the fans in shorter terms then from us or china.
But actualy it depends on seller and the delivery type. I used to receive a Bitmain warranty replacement PSU within a week from china to Eastern Europe by UPS.
