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If the Freon pressure is too low or high, the compressor won't engage. With that, you really need to get a manifold set to check both high and low pressures.
Once you get the manifold connected, you will need to see what the pressures are. Here are a few readings based on ambient temperatures that you should expect to see when testing. They should be very close.
70°F Low pressure 35 - 40 psi High Pressure 145 - 160 psi
90°F Low pressure 45 - 55 psi High Pressure 250 - 270 psi
Let me know if that helps or if you have other questions,
Monday, March 25th, 2019 AT 6:55 PM