Actually, there are 3 settings where the compressor will not operate; vent ( or dash), floor ( or heat) and of course, off.
My '97 Ranger has a factory switch where if the outside ambient temperature is ( I believe) below 50F, the compressor will not kick on in either defrost modes ( dash only, or dash/floor).
wink

'95 Contour SE, Teal Blue
5-speed, 223K, In process of restoring. Loaded. All factory stuff.