Alright, so a handful of you probably know that I've got a shitty low-end PC running Ubuntu with MythTV installed attached to my TV for recording TV shows and general "oh hey look what I can watch... on MY TV!!" guest-impressing dickery. The machine's ran solidly-enough for quite awhile now, and other than a handful of "oh shit I played with the settings wrong and broke linux. " moments and replacing harddrives (one was too small at 400GB, one of the twin 640GBs died several years later, etc) I've had no issues. However, as of late I've had major issues with the 90mm fan at the back of the case: it would simply not spin up for several months, and as of about a week ago it's started spinning up and then quickly reaching what I assume is maximum velocity - it's rather loud, after all - and then spins down, only to repeat the process. The noise is rather annoying as I'm sure you can imagine, and as this box sits in the living room loud noises simply will not do. Googling the problem has yeilded no useful results; all I can find is help topics on forums regarding PCs where the fans spin up then rapidly spin down without booting. Does anyone have any insight as to a solution for this problem? I'm out of ideas myself!
The fan's speed controller is broken. It needs to be replaced. I had a CPU fan get stuck on highest speed once—it was horribly annoying and just had to be replaced.
I wouldn't exactly say that. Speed is controlled by the motherboard, if at all. All the controller INSIDE the fan does, is give the BIOS the RPM it is currently having. Carefully take off the sticker on the back of the fan, and get some knit-machine oil and pour some of it inside the fan. Put the sticker back on, and see if it is still that loud. Cheers Oerg866
Eh, but the fan has a controller in it which receives those commands, if it's the right type of fan. One type uses the BIOS to control, the other has a self-thermistor based system. If it's the latter, then this behavior means the internal speed control circuitry is broken, as it was on my CPU heatsink fan (which had its own thing just like that.) On the other hand if it's a BIOS controlled fan then it is either dirty or a setting in BIOS is busted. Maybe the cable is loose.
Metal Man88: I'm sorry, but that's like the call center computer company support saying "reboot and try again". Let's consider some technical facts to actually help people for a change: Such fan controlledness only applies to newer 4-PIN CPU Fans. Case fans use the regular 3-pin connector. A thermal diode inside a fan Won't help because it is too far away from a significant point of heat to warrant spinning up or down. (not to mention case temp isn't really that crucial to proper operation) The only thing happening there is the pulsating signal coming from the fan signalling the RPM. A busted BIOS Setting, unless some bright person got the brilliant idea to mess with the bios, cannot happen either. Only possibility would be that activation temperature == "CASE FAN TO 100%"-temperature. Some BIOSES offer this setting. Try loading the default settings to find out. A dirty fan would not cause the fan to suddenly roar up. A loose cable cannot cause sudden roarage aswell, since due to the metal connector thinning towards the other end, it will either latch in place or not touch at all. Also, your computer might have bad capacitors or the likes. Check your motherboard for bulging/leaking capacitors and also try a different power supply, incase ripple current is causing the fan control to malfunction.
Hm, well, the thermistor thing I said is only correct for CPU fans, since I forgot the obvious problem of it being nowhere near heat, so yeah. It's limited to whether something really weird junked the BIOS setting for it or the other stuff Oerg said. I have a nice dirt-filled case fan which acts erratically too, though it doesn't speed up—it just makes a lot of noise if the dirt inside it is disturbed (say, by attempts to clean it out.)
