Air conditioner compressor noise
The noise you hear from the a/c compressor when it is first turned on is caused by where the compressor is located. I bought a new 2004 Ex pedition and it made this noise Ford calls (get this) CHUGGLE. I brought the truck back to the dealer so many times and was a pain in thier ass they finally printed out the service bulletin. It said "this cannot be repaired if you try to repair it, it will still make this chuggle sound and Ford will not reimburse you for the work if its under warrenty". The sound is caused by the liquid refrigerant and oil collecting in the compressor under certain conditions. Because the compressor is the lowest point in the system, poor engineering. The shop manual addresses this issue, in the manual its called "slugging". Ford was supposed to program the ECM to engage the compressor clutch while the engine is cranking to push out the liquid and oil slowly. Apparently this doesn't work. the dealer said this "will not hurt the compressor". I just retired after being an auto and truck mechanic for 47 years and this is BS the compressor is very delicate and won't take that for too long. It happens when the sun heats up the interior of the car causing the gas in the a/c system to expand forcing the liquid into the compressor if you notice this don't happen at night or in colder weather. To prevent it and save the compressor shut off the a/c before you park the car for several hours, when you restart the car DON'T turn on the a/c until the engine has fully warmed up, about 5 minutes. Hope this helps