I have a 2002 Ford Explorer with a 4.0 V6. The AC blows only slightly cooled air. The compressor cycles on and off every 10 seconds when the AC is on. Pressure readings with the manifold gauges hooked up and the AC running ranges from 18-45 psi on the low side and 95-100 psi on the high side. With the AC off both gauges register 75 psi.

I checked the connection on the cycling switch and it looked OK. Is it time to replace the switch or could it be something else?

 

Depending on the temperature you tested at,t he pressure on the high side sounds low. At 90 degrees should be around 150 psi on the high side. The pressure needs to be checked against a temperature chart, the pressures required varies by the ambient temperatures.