I had this same problem on 1997 k1500. The A/C button and air flow selector did not work. After replacing the AC controle Module, ($200 AutoZone) i found that the A/C button and air flow selector only worked when blower speed switch in "off" position. Based on the second link in your post "Problem #1:
If:
a) air flow is always directed to the floor, regardless of the position of the Mode dial and,
b) the
AC button does not illuminate when depressed and,
c) the Recirc button does not illuminate, and the resirc door does not operate and,
d) the AC compressor does not come on;
This is caused by an open Switched +12V
power transistor, or it could possibly be caused by a defective blower speed switch."
i concluded that the switch was bad from AutoZone so i replaced it again. No change
The manufacture wires the switches wrong. I checked 3 different units from AutoZone.
i was able to move a wire in the blower speed selector wiring harness and give the A/C button and air flow selector power when ever the ignition is on.
see photos for more. Take the blower speed switch wiring harness off of the switch and remove the 2 blue wire keepers. remove the Green wire in terminal "D". replace it into terminal "E". (Here i had to replace the entire pigtail because some of the wires were burnt and the plastic broke apart.) To confirm, you now want the Green wire (that goes directly to the other plug into the back of the AC Controle Module) to be connected to the terminal immediately below the one that it came off of. This is the only terminal that is visible connected to another "G" inside the switch.
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