Could be a vacum leak, the idle thing might be normal, i dont know about honda as i have not been able to use my a/c yet...but my wifes xterra does that because it requires more to keep the a/c going, when the idle drops to low the car brings it back up to the right rpms to keep the a/c going. If not blowing all the time could mean you need to recharge it..is the air just not cold and still coming out or is it not blowing out?
Could be the compressor since you said it squealed... another thing is your car overheating at all?
Check the freon level with a manifold gauge while the car is idling. There are two connectors under the hood attached to your A/C's refrigerant system that should be labeled as such, one for the high Psi end of your gauge (the red side) and one for the low end (the blue side). If the level is unbalanced, it will cause the entire air-conditioning system to shut down as a protective measure. If the level is low, you may have a leak that needs to be fixed as soon as possible.
Turn on the air conditioner and lift the hood of the car to check the compressor. Many problems can occur because of an old or malfunctioning compressor, which is often diagnosed by the different sounds your car makes. For example, a grinding gear or a sudden screeching sound of metal could indicate a problem with the clutch, while a banging sound near the engine may mean the compressor is wearing out and should be replaced. If the compressor keeps turning on and off, the freon level is at fault. If it doesn't turn properly, the problem may not even be related to the A/C, but the power itself.
