Auto Air Conditioning & Heater Repair: 97 Tahoe a/c, side switch, psi

Question
I had compressor,drier,o'tube replaced,system flush,vacume done. The output at the dash is @ 42 deg near an outside temp of 78. However,during hwy use the return line near the compressor has a  frost build up,and I have yet to see the it cycle yet.Seems to blow cooler air when driving as well.Hi side doesn't exceed 230.low side between 25-35 @ 2k rpm while sitting in driveway.I ohmed the low side switch,closed when pressurized,open when removed. Is the system overcharged? Will this cause it not to cycle? When doe the low side switch kick out the clutch at what pressure?

Answer
HI Garry

Your cycling switch will not kick off until your low pressure hit 18 psi or so.  At idle bring your RPM's to 2000 and hold it there if you see your pressure drops below 15 psi and your compressor does not turn off then your cycling switch is bad.  You may see a little bit of frost and then the compressor will turn off and the frost will go away.  If you need anything else let me know.