Rosewill RCX-Z2 spins up and down every 45 seconds, WORRY OR???

[weatherphobia]

Rosewill RCX-Z2 has been used since early 2013 for my Q9400 intel system. Now it ramps to 3500 RPM then 45 seconds later jumps down to 3300 RPM, then 20 seconds later back to 3500 RPM.

Like a Sin Wave on an oscilliscope, has been doiong this for 3 days.

Worry or not?

 

[C12Friedman]

I would venture that it is time to take the fan off the unit and blow it out real good with compressed air. I'm thinking you should be able to get it clean without removing the HSF assembly, just the fan. It probably wouldn't hurt at all to remove the entire HSF though but you will then need to clean off the old and apply fresh thermal compound to the heat sink. See where you get the easy way, if the fan speed still fluctuates then I'll recommend removal for cleaning.
Hope it helps