Solve : FAST/S'OW FAN?

1.	Solve : FAST/S'OW FAN?
Answer» As the title says' my fan keeps speeding up then slowing down.i have recently INSTALLED this fan it is only a cpu case fan. but while i had it to BITS i decided to clean the heatsink and replace the thermal paste .i read how to do this and i followed the instructions correctly (i think) ANYWAY everything worked ok .but after about a week the problem started. any chance you can solve this for me. thank you.How is the fan plugged into the computer. DIRECT from the POWER supply, from a fan header on the motherboard or other . Does the fan have 2,3 or 4 wires in it's cable and are all the wires connected at the supply end? even if new i wouldn't trust the fan...replace it....

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