Tango Yankee

When I start the AC there is a loud thump from under the dash, like a vent damper closing. It is 100% not the magnetic compressor pulley kicking in. The thump is definitly too loud and will need fixed. 2013 GMC Sierra 1500 SLE Thanks.

I'm trying to find a trailer brake controller for my 2013 Sierra 1500. None of the popular manufacturers support a controller for a 2013. I'm assuming that this is because of liability. However, I suspect that there are several controllers out there that I can use but no one will list it. I'm looking for a simple time-based controller that I will not be using a lot to tow a travel trailer camper. Does anybody recommend a controller? Thanks.