Scott – thank you for your reply. I thought about the fan being the culprit. However, changing the fan speed doesn’t affect the noise at all. Also, at least in my case, the fan doesn’t make any noise when stationary. I do hear the grinding noise under acceleration as well. When I let go of the gas the grinding noise becomes easier to be heard due to less noise coming from the engine.

Yes, when I turn the fan off or reroute the air to top and bottom vents (take a face/middle outlet out) the sound disappears. But the grinding/cricket noise does change with revving the engine.

britcon - Thank you for your comment. You might be very well right. However, I like to know (if anyone knows this) do you think revving the engine with change the air inflow to the blades of the HVAC fan? If that’s the case, the fan bearing can be the cause of the noise. How expensive is it to change the motor???

PropellerHead - Thank you for your comment. The noise is coming thru the middle (face) vents. Plus, it can’t be heard when stationary and changes with the engine rpm.