A/C compressor?

A/C charge should be 22 oz. It may be overcharged. Put a gauge set on it and see what the pressures are. You did pull a full vacuum as well? Asking because if there is air or moisture in the system it could also act this way.

What do the pressures do if you jump the wires, so the compressor engages? If they stay the same on both sides the compressor isn't working. If there was a blockage but a working compressor you would see the low side get drawn down to 30 or less but the high side would go far higher than normal. Then when you disengage the compressor, those pressures would stay that way for a while because the refrigerant pressures wouldn't be able to equalize due to the blockage. 134A static pressure should be close to the ambient air temperature. If you connect up and see the pressure on the system is say 90 and it is 91 degrees, then it has some 134A in it.

Where are you getting them? What is the pressure if you just connect the gauges with the engine not running? About the only other thing that could cause it would be if the orifice tube is the wrong one. If it was too large it wouldn't restrict the 134A enough and you would get a narrow pressure window like you have. As for the pressure switches, the low pressure is a simple switch, If the system has any pressure in it that switch should be closed. It opens when the pressure drops. It simply grounds the circuit so if you unplug it and use a jumper to ground on the A (blue) wire that would be the normal position of the switch. The high side is a true pressure sender. You should have a ground through the computer on terminal 1 (black wire) then 5 volts on terminal 2 (gray - your green wire) and terminal 3 (red with black) is a variable voltage that tells the ECM the system pressure. It controls the clutch cycling by adjusting the pressures in the system based on exterior temperature and A/C demand.
Is this an automatic system where you just set a temperature or the manual system?

Hmm, those pressures are low. 82 ambient temperature I would expect the low side to be around 45 and a high up around 200. Then with the engine off in 82 degrees you would see about 82-85 psi on both once it equalizes.
What was the reason for compressor replacement? 18-20 psi won't even close the low side switch. Try this, unplug the low side switch and jump the two terminals in the socket. Does the system now come on? If yes, then it might actually be low on charge.

Yeah, it won't work without the pressure switch. Normally the valves stay closed unless you are pulling a vacuum or charging the system. You connect the gauges then open the valve in the coupler on the hose. Then barely crack the low side valve on the gauges and it will purge the air, then close the valve. Repeat for the high side. Both of the valves on the couplers should be open and the valves on the gauge body should be closed. They then will show the low and high side pressures. If you open both valves you equalize the system, and the compressor just goes into a loop. As that switch is leaking it is likely that it leaked out some of the charge as it sat as well so you might want to have some standing by.

Okay, sounds good but if you had metal flakes I would have a shop recover the charge you put in, then pull the orifice tube and check that it is clear, and install a line filter so that the flakes get removed and can't clog the orifice or circulate back to the new compressor. Those floating around can cause problems and even if you flush the complete system, some still seem to stay behind.