I have a humming sound coming out of my dash sounds as though it is coming fm the radio It starts when you turn the switch key on and humms till several minutes after you turn the key off very annoying anyone have any thoughts on this? 2001 S80 2.9 non turbo I raised the hood and you cannot hear it It is coming out of the dash about where the radio is It does this even with the radio off

 

Just fixed it. The little vent on the dash board for the return air flow had gotten clogged with lint crud and what ever took a vacaum to it and you would not believe what I got out. Had to take a tooth pick and pull some of it thru the little grates. Put the vacaum over the hole as tight as possible and you will be surprised what is in that little hole