Using HWmonitor I can see that my CPU fan is randomly dropping to 0 RPM for about 1 second.
I have no idea what is causing this, but it's been happening since I built the rig back in June.
What I want to know, is if it's completely normal? Is this a buggy reading, or something to worry about?
There are no temperature fluctuations during the drop.
None of mine do that. It could be a bad sensor, signal, or connection between the fan and the motherboard's power connector. With the computer power cord disconnected, remove the fan connector, clean the montherboard's pins with a coffee filter paper just barely damp with rubbing alcohol. Wait a couple of minutes for any remaining alcohol to evaporate. Then reconnect the fan power lead to the pins, reconnect the computer power cord, and power-on the computer.
With luck, cleaning the pins solved your problem and it won't happen again.