Subaru Repair: Subaru AC Noise, pressure hoses, subaru outback

Question
I have a 2003 Subaru Outback wagon with 56,000 miles on it.  About 5 mos. ago, the AC went out.  I noticed that it would not de-fog my windows on rainy or cold days.  It made a hissing sound & no cold air came out of it.  Took it to the Subaru dealer where I bought the car new 4 years ago.  They diagnosed it as leaky high and low pressure hoses.  After some price negotiations, I finally got it fixed at the Subaru dealer about 2 weeks ago.  Now the AC occasionally will make this low-pitched moaning,groaning, whining sound.  If I turn off the AC, the moaning/groaning stops.  And sometimes, it doesn't make the sound at all.  The AC is now cold, blows good, etc.  What could be making the low pitched moaning/groaning/whining sound? If the air is working, do I just put up with the sound? Or is this sound indicating something else is wrong with the AC besides the high and low pressure hoses?

Answer
There are many problems you could have.  It could be an easy problem, for instance if the dealer didn't give the a/c system a good vacuum, the system could have air in it and that can cause a compressor to be noisy, or they have an incorrect charge of freon or oil in the system. You could have a compressor going bad.  The problem with that could be, the compressor could have been going bad before the leaks in the lines were fixed, or the system wasn't flushed and there is trash in the lines causing bearing failure in the compressor. I wouldn't be took quick to blame the dealer, but I would take it back and have them check it out.