Sensor Inputs
WARNING: This page is about a different car, the 2015 Ford Fiesta. However, it is still accessible from the selected car via links, so may be relevant.
The Ambient Air Temperature (AAT) sensor and the evaporator temperature sensor are inputs to the IPC. The A/C pressure transducer is an input to the PCM. If the temperatures are below a predetermined value, or the system pressure becomes too high or too low, the PCM does not allow the A/C compressor clutch to engage.