Question 970 GTX Last fan suddenly stops/starts spinning for no reason

[mhmarefat]

In the name of God.
Hello.
I have a 970 GTX (g1 gaming from gigabyte) used for less than 2 years. Hadn't installed any drivers/updates on PC yet suddenly last fan (near the ports) stops spinning causing other two fans to go full speed. This happened while I was in middle of a very light and GPU-stress-free video game (recently played Metro on ultra presets with good FPS. had no problem).
After a few reboots it suddenly fixes itself without me doing anything. This happened 2 days ago and I haven't played anything GPU demanding game since, fearing a damage to the card should fan stops spinning.
Did a clean re-installation of GPU driver to no avail. Also my motherboard is Asus Z97-pro. (BIOS of both are factory-default).
Also worth mentioning when this happens, under Sensors tab, "Fan Speed (RPM)" shows "0" while "Fan Speed (%)" shows normal values.
Could anyone help me find the cause of this problem?
Thank you.

 

[jay32267]

I think it sounds like the fan motor may be failing. They aren't made to last as long as I'd like them to.

"stops spinning causing other two fans to go full speed. "
I think this is probably because the temp rises when that one fan quits and the other two are trying to make up the difference.

I would look at getting a new fan/motor assembly.

 

[mhmarefat]

This card has worked for almost 2 years.. don't think it's a long enough time to pass its lifetime..
also other two fans go to full speed when GPU temp is as low as 39 C..
So it's possible to replace that one fan entirely? You'd recommend I do that?