1999 Explorer Limited, v8, 2wd, climate control, Florida

Yesterday evening when we went out the air didn't seem to be very cool.
We didn't go far so I just brushed it off. Today, in the heat of the
day, it seemed to be cooler outside the car than in it. I just did
minimal investigation, I started the engine and looked at the compressor
clutch. The clutch cycled at about 3 second intervals in and out. I
disconnected the pressure switch (?hi or low?) and the clutch
de-energized completely until I reconnected it.
Any ideas before I spend 'big bucks'?

TIA,
Dave
--
Diving is life! The rest is just details.
W.W.W.I.