Strange A/C behavior

[82chevdiesel]

Im having some strange results with my ac in my truck and am not sure what is going on. With the blend door set to cold I am getting cooled air out of the vents even with the ac turned off. The bizarre thing is that there is no electrical problem, the ac compressor is disengaged as it should be but I am still getting super cooled air. If you feel the ac piping it is also very cold to the touch dripping wet with condensation and sometimes even frosted. At first I thought there was a leak, but this has been going on for months now and the system has been leak tested. Also when the a/c is switched on it does work properly.