Ac Compressor Power Plug

[BC77]

Hello all. 2009 international prostar with Cummins isx. Been having issues with ac every summer for the last few years. I replaced everything new and flushed out all the lines. I'm not getting any power 12v to the plug that plugs into the ac compressor. My 2 thermresistors are reading 2100 ohms and when I apply 12v from my power probe everything works fine. Any ideas and does anyone know if this controls the plug, see pic? Thanks