No it`s not another "how do measure sub cooling etc" question. Well not exactly. I`m just asking as I`m pondering how s/heat and s/cooling are measured when there`s as fan pressure switch that obviously causes the HP and LP ( to some extent) to rise and fall. Do I need to restrict the airflow over the condensor to keep the fan running, and hence the pressres steady, or do I take the midway point on the HP and LP gauges, and on the temperature readings.

Thanks in advance for any ideas,
Glenn