I have the same problem that I have seen posted by others here. The issue with the a/c blowing hot air when it should be blowing cold! I have heard it is an issue with a vacuum check valve which keeps the cold air flowing thru the system. If you rev the motor during this HOT flash of air, you will hear the door slap shut and the cool or cold air will flow once again. This seems to be a serious problem with ALL of the diesel for trucks from this same period. I suppose since it is not a safety issue, the will never be a recall on the part causing this problem.