'91 Buick Park Avenue, A.C. goes to economy when "auto" is selected. All other climate controls O.K.

I selected the "Economy" setting on the climate control, afterwards, I cannot select "Auto" for air conditioning. When I push "auto" it will light and beep when I press the selection, but as soon as I release my finger, "economy" lights up. No A.C. All of the other functions work properly, with the exception that the comperssor does not run at any time, when on "auto" or on defrost, and the air is channeled to the proper vents. The car has the dual A.C. option, and the compressor will run when a hot wire is run from the battery to the low pressure switch on the aculator. The system has a programmer, which I am guessing may be at fault or the control head. I would welcome any of your ideas or insights on how to troubleshoot, or what the problem is if antone has had a similar experience.