If it does it with the AC off, I wouldn't think it's the compressor. Remove the serp belt and start the engine to see if the noise is gone with the AC not spinning. NOTE: Only run the engine a very short time without the belt. It will overheat.
If the noise is gone without the belt, then the compressor may be it. However, everything you have described sounds like the blend door is not working properly.
Let me know what you find.
Wednesday, September 15th, 2010 AT 9:03 PM