Littlehorse, I found this on my Ford CD that I forgot I had. See, I told you I'm gettin' rusty. Now I know where to look.
(The A/C cycling switch (19E561) is mounted on a Schrader valve-type fitting on the side of the suction accumulator/drier (19C836) in Aerostar vehicles, and on the top of the suction accumulator/drier in Ranger and Explorer vehicles. A valve depressor, located inside the threaded end of the A/C cycling switch, depresses the Schrader valve stem as the A/C cycling switch is mounted and allows the suction pressure inside the accumulator/drier housing to control operation. The electrical contacts are normally open when the suction pressure is at or below 23±1 psi; they will close when the suction pressure rises to approximately 40-60 psi or above. Lower ambient temperatures (below 8°C or 46°F), during cold weather seasons, will also open the contacts due to the pressure/temperature relationship of the refrigerant in the system.) The compressor cycles normally in summer so the switch is functioning. Why it won't open in winter is the question. No big deal, just cabin fever setting in. I need something to tinker with.