I just had my AC system replaced with new compressor, expansion valve, condensor, o-ring kit, Etc. My system works fine now but there is an annoying squealing noise that is coming from behind the glove box. It only does it when the AC is on not just the vent. I replaced the blower motor and it is still there. It is intermittent but consistant. It almost sounds like letting the air out of a balloon with the sides pulled. Any ideas??????

 

sounds like the new expansion valve is the wrong size.