GMC Repair: GMC A/C Nightmare, gmc sierra, exact answer

Question
I have a 1992 GMC Sierra 3500.
While hunting down the cause of my battery going dead, I pulled the connector to the compressure and the clutch disengaged. Yes the key was out. Also found that after turning off the Truck the blower was still working but would shut off after pushing the off button.It seems to cycle often but will cool nicely .Perhaps there is two problems?. The only code I get is 12. Alls well if I remember to hit off and disconnect the compressue every night but perhaps you can point me in the right direction. Thank you......Mark

Answer
I don't have access to the schematics to give a exact answer, but I will tell you what I would try. Try unplugging the A/C controller and see if the clutch disengages. If it does, then either the controller is keeping it on and has an internal failure, or it is still getting power with the key off when it should not. If it is still getting power with the key off, you  may have a faulty ignition switch.


I am sorry that it took so long to reply, it has been very busy around here.