So I decided to upgrade from my trusty Arctic Cooling Freezer 7 Pro Rev.2 to a True Spirit 140 CPU cooler and I decided that, as you can, I'd run twin TY-147 fans in a push-pull configuration using a PWM splitter from the CPU Header. We won't talk about the wire clip fan mounting system, because just thinking about it makes me want to commit mass murder, but we will talk about why it just does not want to work properly. Using an Akasa PWM splitter attached to the CPU Fan header, the fans won't spin up or sometimes one will get going but the other won't. Connect a fan to the Sys Fan header and it starts spinning then stops and looks like it's trying to spin but can't get going. Connect one fan to the CPU Fan header and sometimes it will spin up, other times it will start, then stop and then look like it's trying to spin up but can't. I've tried setting the fan control to PWM and Voltage in bios, neither makes any difference. What am I doing wrong?! It's so flipping temperamental - it was working ok for about a week, though possibly just one fan was working, can't see them both without pulling the side off the case, and today it stopped and neither fan would work. Even when I plugged them in individually to the CPU Header they didn't want to work and even the Sys Header couldn't get them going. Are they not getting enough power? It's driving me absolutely crazy. Help!
Does it do this only when your CPU temps are low, or even when under load ? A fan cannot start with a too low PWM signal as it doesn't get enough power to overcome the step to the next coil, but this shouldn't matter when the temperature gets high enough so the PWM signal gets longer.
As John_Edward said, it could be your motherboard slowing the fans down when the CPU temp is low. Fire up Prime95 or Intel Burn Test along with Core Temp (or Real Temp if you have an Intel CPU) to keep an eye on the temps. If the temps start shooting up and the fans still wont spin then its likely there's a problem with your motherboard. If they spin up and keep the temps within a good range, then the motherboard is slowing the fans down when the CPU temp is low enough (what are your temps at idle?). To rule out faulty fans, try connecting the fans to your PSU directly with a 3/4 pin to molex adapter:
PWM = pulse width modulation. http://en.wikipedia.org/wiki/Pulse_width_modulation Basically what happens is the voltage is sent in pulses. IE it isn't constant. So the way it works to control a fan is to send the pulses at different rates in order to make the fan spin faster or slower.. Due to that you are sending that PWM signal into two fans. Either one will get the signals and work fine (with the other one throwing a spazzy) or neither will work correctly. People with PWM fans have had issues with some fan controllers (that are not PWM and send a solid controlled voltage) with a buzzing sound. If you can connect the fans to their own headers with no splitter. If not? then use a molex to 2x3pin and if the fans are too loud at 12v get some resistors (inline) to quieten them down.
Thanks for the replie guys. So, for example, today my fan didn't start the first two times that I turned my PC on (my CPU fan alarm started going off) but on the third time, when I had the case open and was watching, it started spinning straight away. Once it's running, it works fine. Should it spin up straight away? With my Freezer 7 I had the fan control set to auto and the fan would start virtually the moment that I powered up the PC. Is it normal for the fans to only come on when CPU temps rise? Will these fans work with the bios fan control setting set to auto? Sorry for all the questions but I just want to figure out the best way to connect everything up to get both fans working. It sounds like the PWM splitter might not be the way...
So, I worked out what the problem was. It was me. Because the fans weren't spinning up straight away and the CPU fan failure alarm was going off, I was panicking. Today I decided to ignore the alarm, let the PC boot up and when I checked the core temperatures they were nice and cool and the fan was spinning. As I wasn't used to PWM, I was worried when it didn't spin up to speed the moment I turned the PC on. I just plugged in the PWM splitter and both fans are spinning away happily! Job done, panic over
