03 Expedition AC grind noise at startup

I have a 2003 Ford Expedition that just had some AC work done. Now when I first start the car and turn on the AC, I hear a load grinding noise that lasts about 2 seconds and then goes away. It is obviously coming from the AC. What could it be now?

ford has a message about this - the noise is normal after sitting - caused by oil building up in the compressor - if it does it more now than b4 the work they problably have overcharged the oil causing it to settle into the compressor - it shouldn't cause problems but you can take it back and see if they can evac the ssytem and removed some of the oil.