I took my 99 Expedition (4.6 liter) to the dealer the other day. They said that my air compressor is leaking and that they would replace it for $100 an hour. The job is said to take 5 hours. The problem I am having is that my air conditioner blows hot air in the front but it is cold in the back. Now is it truly an air compressor problem or could it actually be another problem that they are not telling me in order to get me to replace the whole compressor. could some one let me know. And also if it is the compressor, how difficult would it be for me to replace it myself.