When I use my laptop while the A/C is on (temperature around 27-28), the fan starts making a grinding noise. This does not happen when the temperatures are high. Further, the CPU's temperatures are around 45-55 when idle.
What I am thinking is that at low temperatures, the fan begins to rotate at a particular speed that causes it to make this noise. When the temperature increases, the noise disappears because the fan starts spinning more rapidly. Some sort of resonance issue, but I may be dead-wrong.
Any suggestions? I took the laptop to the service center but the fan failed me there (made no noise). They simply got rid of the dust in my computer and gave it back to me.