If you have the climate control heat/AC with the Auto setting your fan is a variable speed unit that has solid state controller. Very common for this controller to go out. The unit is mounted under the hood about 12 inches to the right of the fan motor. directly back from the right side valve cover. The unit ia about 4X2" with a connector on the right side. This unit can only be purchase at your dealer. difficult to change but it fixed my problem.