Fix stuttering and pulsing fans - Computers & Internet

First I would see if they are overly dusty. If you open the case and blow the dust out with compressed air, this can help.....fans can sputter quite a lot if they have an excess of dust which happens all the time.

If getting rid of the dust does not help, it is likely to be either a power issue, or a controller issue.

so....next, try re-seating the power cables that come off of the sputtering fans, and make sure they are plugged into the right spot on your motherboard (your motherboard manual should have this diagrammed) and make sure they are fit snugly to the connector. The fan could also draw more power than your power supply can handle, therefore you could be in line for a new power supply.....if the fan worked well previously and just started this sputtering it could be due to a new piece of hardware (have you upgraded anything?) that could be drawing more power from the power supply.

If neither of these is the case, many motherboards and chipsets have built in fan controllers...Basically they are supposed to automatically adjust the speed of the fan based on how hot it gets inside the case. This keeps the fan on lower power (and thus quieter) until it gets to a point where it has to run higher because of more heat. These controllers can sometimes go a little haywire, or the heat sensors can fail.....you may be able to enter your system's BIOS and manually change the fan settings to prevent the sputtering.

If it is not dust or power, you may have an issue on your motherboard which is a larger problem, that you may want to have a local tech look at. (if you feel the PC is worth fixing for what they will charge you)

Clean them or replace them.