With reference to the diagram, I am assuming it is necessary to have a 12v feed to the A/C Thermostat switch labelled Black, then when the knob is turned on (it clicks on when initially turned) this switches the 12v to the Blue wire and onto the Binary / Trinary switch?
Then adjustment of the knob dictates the temperature the compressor switches on and off.
Then adjustment of the knob dictates the temperature the compressor switches on and off.