OK. I tried the AC using the top button of the three vertical buttons, the button next to the off button in thr horizontal row of buttons temp wheel all the way in the blue and locked and fan on high. Nothing but hot air. With the buttons at the listed settings and I press the off button and the one to its left ( white rectangle box with two small black boxes on the button) I can hear the engine slow. I assume that is the compressor kicking in. Where is the low pressure switch located and how is it checked? Thanks in advance.