Their are two possible uses of static pressure that I know:

1) Check the refrigerant for contamination w/ air. If system pressure is much higher than it should be for the ambient or system temperature, then air has contaminated the refrigerant. It needs to be replaced.

2)Pressure reference for gauge accuracy. If you know the system is filled w/ pure refrigerant, then the ambient (if ac system and air are at same temperature, this requires overnight wait) temperature tells you what the internal pressure must be. You can calibrate your gauge to that pressure or confirm your gauge is reasonably accurate, say +/- 3 psi.

Other than these purposes, static pressure readings are not of much use for diagnosis. They tell nothing about the amount of refrigerant as some fervently hope when they report the system has "plenty of pressure".

regards

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