I think I remember a month or two ago, someone was having problems with their A/C. I said I would post the diag procedure, but it took me quite awhile to find it and I eventually forgot. Here it is in brief, FYI.
1. Ign off
2. hold A/C OFF and AUTO buttons down and turn on Ign
3. after 9 sec diag starts

1. Ign off
2. hold A/C OFF and DEF buttons down and turn on Ign
3. resets A/C and clears faults

A list of codes is displayed if there is a problem. Otherwise 00

There are other things that can be done during the test to test specific things. Too complex to post here.