central air unit

My wife and I recently noticed a burning smell. We didn't pay any attention because it disappeared soon after. Then, while I was at work, my wife notices that the smell is coming from the inside a/c - furnace. She also tells me that the unit itself is hot. She turned the air all the way off, but the fan is still very hot to the touch.

Any ideas as to what might causing this? The unit is a 10 year old Nordyne, model # C3QA-03U-B, ser. # C3Q9606-55530.

Fan model # E1EB015HA, Ser # E1E9604-06196.

Any help will appreciated.