Auto Air Conditioning & Heater Repair: DODGE DURANGO AIR COND NOISE, metal shavings, dodge durango

Question
2002 DODGE DURANGO 4.7 HAD NOISE THAT SOUNDED LIKE A FOG HORN IN AC WHEN COMP WAS ON. COMPRESSOR WENT OUT AND HAD IT REPLACED BY REPUTABLE MECHANIC SHOP. NOW THE NOISE IS LOUDER THAN BEFORE AND WHEN IT DOES IT IT SEEMS TO BE CAUSED BY VIBRATION OR PRESSURE IN HIGH PRESS LINE BUT DOES NOT DO IT ALL THE TIME.

Answer
Rusty,
My first question is how long ago was this compressor replaced?
When they replaced the compressor did they flush the system or replace the orifice tube and receiver? If the compressor burnt itself out then it sent metal shavings all through the system. These should have been flushed out. When they replaced the compressor did they add oil to it before installing it? If you are able to answer these for me, it would help out quite a bit.
My first thought is always the easiest. Is your belt tight? If it is skipping over your compressor, the compressor may be "shuddering" and as it turns it would feel like a vibration in your high side line.
The second thought is that your clutch is slipping. Have your shop check the air gap between the clutch and pulley. This is usually set from the factory where the compressors are made, but it does happen. The clutch slipping would act exactly like a belt skipping over the pulley and cause it to "shudder"
My third thought, and I hate to think it, but your shop may not have added the oil to the compressor before installing it. This will cause your compressor to go out again. 99% of compressors that you get from an auto parts store comes with oil in it. But this is nothing more than an assembly lube. It is NOT the actual amount of oil your compressor and system needs to operate. Aske them how much they added prior to installing the compressor.
If these three possibilities check out get back with me, and I will dig further in. But before you get back with me, see if you can get your pressure readings from your high and low sides. Both while it is and is not sounding like a boat lost in the fog. Pressures are the basis for the entire A/C system and you may be surprised by all that they are able to tell a technician.
Thank you for your question, and I hope I was able to help a bit. Good luck.