All of you Northerners who are in the below zero weather:

Is your NBS (mine's an 07) howling when starting it up in the negative degree range? I have narrowed it down to the AC compressor, as it won't howl when the defroster is not on.

Should I have that looked at? Is it normal? It goes away after the truck warms up. -6 this morning here in Central Iowa.

Thanks.

 

not much of help, but, most likely, they copied what Japanese makes had long before - AC turns on automatically when you switch to defrost mode. Helps remove moisture out of the cabin air faster, but is very annoying and can be bypassed on Hondas and Toyotas. Donno about GM, ask dealer.
But, it sounds like magnetic AC clutch might be developing some sickness.

 

My 2007 NBS did that about 4 times last summer here in Texas (100 degrees) but I haven't heard anything in 6 months! I came to the same conclusion as you, but it stopped so it's not broke!

Charlie