Case fans randomly start and stop spinning

[astrosteve]

For about a week now, my desktop has been behaving oddly. My case fans unpredictably start and stop working. Sometimes I turn the computer on and they don't spin up. They start spinning if I manually spin them (usually via a quick blast of compressed air aimed at the fan), but not as fast as they should be (I can tell this just by looking at them) and my computer quickly overheats. If I run SpeedFan to see what's going on, it reports them turning at impossible speeds, anywhere between 20,000rpm and 250,000rpm. Obviously, there's no way a fan in my case is spinning at 250,000rpm. So, the fan speed is reporting incorrectly as well.

Other times, I turn the computer on and everything is fine. Fans spin up on their own and SpeedFan reports normal looking numbers for a case fan. The weird thing is they work in unison. They either all spin or none of them spin. I've never observed only some working.

Interestingly enough, one of the fans on my video card died at the same time. Won't spin no matter what, even when the case fans are working. It's a video card with 2 fans on it. One works all the time, one is totally dead. As luck would have it, I had just ordered a new video card so I'm not too concerned with figuring out what's wrong with the video card because I'm replacing it anyway. (I got a new 4k monitor and as it turns out, R9 270s cannot handle gaming in 4k resolutions, so I needed a new one.)

But the 4K monitor is the final thing I need to mention: Everything stopped working after I got a new monitor. I don't see any way a monitor could fry my system fans, but it sure seems like it did. Also odd is the computer rebooted for some reason while I was plugging the monitor into the computer. I didn't do it or anything. Again, I don't see how a monitor could do this, but it sure seems like the monitor caused it. All these problems started happening as soon as I plugged the monitor into the video card.

Does anyone have any idea what's going on or how to fix this?

My computer's specifications as well:

Case: Corsair Graphite 230T (With stock fans on it. Two in the front, one in the back)
Motherboard: Asus M5A97 LE R2.0
PSU: Corsair TX750
CPU: AMD FX-4130 3.8ghz (the CPU fan has not had any issues)
Memory: Corsair Vengeance 8GB DDR3 1600 (1 stick)
GPU: EVGA GEForce 1070 GTX
Monitor: Asus PB287Q 28"

The machine itself was built in 2014, and the GPU is the only part that wasn't bought in 2014. In fact, I just installed the 1070 a few hours ago. And yes, I really like Asus and Corsair.

So, does anyone have any idea what the heck is happening here? I thought the fans had died at first, but now that seems less likely. Any idea on how to fix this?

And now, I'm going to go turn my machine on and off a bunch of times and hope the fans start working so I can play Rocket League.

 

[the nerd 389]

How are you controlling the fans? Are you using BIOS settings, Speedfan, or Fan Xpert?

Also, how are the fans connected? Are they each running to a separate header, or are you using a splitter?

What kind of connectors do the fans have? For each of the case fans, is it a single 3-pin connector, is it a 3-pin connector with a single wire and 4-pin molex power connector, or is it a 4-pin fan connector?

Lastly, what connector are you using for the monitor?

 

[astrosteve]

Sorry it took me a while to respond. The fans seem to be working normally now, but I'm still concerned it may be temporary and I probably need to replace something. I use SpeedFan to control the fans. All the fans in the case are plugged into headers on the motherboard. The rear fan uses a 3 pin connector and the two front fans are wired together (which is how they came with the case, I didn't do that) and then run to a header on the motherboard. For the monitor, I'm using a DisplayPort cable.

 

[the nerd 389]

How well is the GPU tightened down? The fan control bus actually goes through the PCIe slots on the side nearest the rear of the case. If the screw were loose, they would be the most likely to encounter problems.

 

[astrosteve]

That's interesting, as I just put a new video card in and the problem seemed to go away after that. My old video card was huge and heavy. It hadn't been touched in a long time. I was plugging and unplugging things a lot when I got the monitor, due to me first using a HDMI cable then changing my mind and plugging in a DisplayPort cable. I could have loosened the video card. I'll wait a bit and see if the problem comes back.

 

[the nerd 389]

I would tighten the screws for the GPU just in case. They should be fairly tight if the GPU is large.

UPDATE: For anyone who wants to chime in on this thread, I'm referring to the SMBus pins on the PCIe connector. They're in the non-lane related section of the PCIe slot. You can see them on the pinout diagram as SMCLK and SMDAT on pins 5 and 6.