A/C Whistle

[Gopens85]

Hello, I have a 2011 Silverado with 5.3 engine and was hoping someone has heard of my issue. I have a whistle/howling coming through my vents only when the air condition is on. It will make this sound in either park or when driving. It does not happen during idle but only around 1000-3000 rpm's. In park, I can get the whistle to hold constantly at 2000 rpm's and immediately will stop when I disengage the A/c. While driving, the whistle will start and continue throughout acceleration up to about 3000 rpm. Any help would be greatly appreciated!

[BAS66]

Make sure your vents aren't closed. This same thing happened to me and this forum saved me from an embarrassing trip to the dealer.

[Gopens85]

Low freon caused the A/C lines to vibrate and cause the whistle noise. Serviced the A/C system and sound is gone! Hopefully there isnt a leak!