The pressure readings are going to vary based on outside temperature, humidity and underhood temperature. On a system that has stabilized I like to see about 30 psi on the low side and about 200 psi on the high side with the fan on medium speed and the ac on recirc and the engine at idle. Like I said there are alot of variables that go into pressure readings so it just isn't "that" simple. In the old days when systems had 3 lb+ of refrigerant you could go off of pressure readings to determine system charge but nowadays 1.5 lbs is considered alot so pressure readings really don't help us much to determine refrigerant level as a system that is a few ounces low may not show on the gauges but definetely affect the cooling performance.
