2004 Thunderbird A/C compressor not running

[JRB4451]

2004 Thunderbird A/C compressor clutch will not engage, no 12 volts at the A/C clutch. I have checked the clutch fuse and there is 12 volts there, the clutch relay and diode are both good. There is Freon in the system and all the A/C controls on the dash are functioning. I need to know where is the low pressure switch is located to verify if it is functioning and are there any sensors under the dash that might control the power to the A/C clutch.
Thanks JRB4451