2000 Ford Windstar A/C won't turn on

Good Morning, My A/C compressor on my van won't turn on. They tell me the freon is full, that the PCM turns on the compressor in "test mode". Both places I have taken it to are continuing to look for the outside air temp sensor. They get a B1254 code (air temp ext snsr failure). No one can seem to find the sensor. My questions: 1) I don't have an indication of outside air temp inside the vehicle. So would I actually have an external air sensor? It's supposed to be located behind the front bumper and no one can seem to find it. 2) If the IAT was bad would that cause the A/C not to turn on due to the sensor showing a cold temp? And isn't the IAT part of the MAF sensor?

Thanks, Rodney