Compressor Clutch
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.
When A/C is requested and all conditions are within normal parameters, a ground is provided to the A/C clutch relay coil from the PCM, energizing the A/C clutch relay. When the PCM energizes the relay, voltage is supplied to the A/C compressor clutch field coil from the relay.