02 Denali Air Comp

Had the Nali in the shop about 3 weeks ago, let me start with I fully trust this mechanic in everyway. It went to the shop for a new fuel pump, but I sent the replacement compressor I bought so they could install it for me. They ended up replacing all 4 shocks as well. Everything was great, and then yesterday the compressor is no longer kicking on right after startup and it's throwing the "Service Ride Control" message at me. The compressor was a Dorman 949-000 I bought off amazon from Dorman. Is it possible the compressor is bad already?

Also, how loud should the compressor be? I noticed on our trip to the mountains over the weekends I could definitely here the compressor right after I started the car when I was outside. I know it won't be silent, but it was surprisingly loud.

Probably not the compressor. The shop needs a Tech 2 or SnapOn equivalent that can read the codes from the suspension computer. There's alot of shops that don't. Take it back and have them read the codes so they can tell you what's throwing the message. If they can't, they shouldn't be doing that work. It could be one of the ride height sensors, the computer, or just a bad ground but they need to read the codes. Mine ended up being a corroded ground at the compressor; you could check that yourself. It's a fairly short wire that goes from the compressor to the body or frame. I've heard the Dormans are pretty loud.

The Dorman is very loud by default. The Arnott unit is whisper quiet. Watch this video, try pulling the fuse or checking it.