I turned on my A/C for the first time since last fall, the air coming through the vents smells awful, dusty and stale. Is there a filter for the outside air coming into the cab? If so, where is it located and how difficult is it to change?

 

sad to say, there is no cabin filter. what we did on my mom's explorer (same concept for SD's) is to cover the cabin air intake grate (the plastic louvered section between the hood and the wipers) with towels, and spray your favorite air freshener in there. douse it good to coat everything. it should keep it smelling good for a while.

 

They sell this odor eliminater at auto parts stores.Works good.It removes mold,mildew,bacteria,algae and smoke odors.You spray it in your in cab air pick up for 15 secs.It smells strong for the frist day or so,but after that the smell is completely gone.
Autozone,advanced auto,pepboys,etc,etc should have it.