The Engine Computer(PCM) activates the AC Clutch relay when it gets the 12volt "demand signal" from the dash switch
In 2007 and up, 12v(fuse 27) is sent out of the dash switch and
THRU the 2 pressure switches to the PCM pin 15
PCM will then Ground pin 14 which activates the AC Clutch relay in engine fuse box
Pressure switch should have a green/blue stripe wire, that's the wire to PCM, if that wire has 12volts then PCM will activate the AC relay
The 12v from the dash switch comes into pressure switch on a green/orange wire
PCM control allows the PCM to shut off AC if engine is over heating(ECT sensor) or if driver wants best power, i.e. Wide Open Throttle(WOT)
It also allowed PCM to turn on electric cooling fan in 2.3l models, with AC on
Ford used a Micro-relay for AC Clutch, seen here:
http://www.gtsparkplugs.com/images/micro-automotive-relay-wiring.jpg
Pull out the relay
85 and 86 slots are the coil hook ups, key on, test both for 12v, only one should have 12v from engine fuse box fuse 43
The other slot is the Ground from PCM, there is no assigned 85 or 86 so can be either way
Start engine, turn switch on dash to AC
Test if this "other slot" is a Ground
If not then PCM is not getting the 12v from dash
If so then PCM is seeing the 12v so pressure switch is not the issue
Key off
Test slots 30 and 87, only one should have 12v, from fuse 25 in engine fuse box
The other one is the OUT to AC clutch coil
If you were to jumper these 2 slots together the AC clutch should activate, "click" if its working, engine or key on or off wouldn't matter, should still click as the coil becomes a magnet and pulls the clutch IN