A/C System Check

[DonSor]

I've worked with A/C systems for many years but mostly in commercial and residential applications. My questions pertains to the head pressure. In any A/C system when the ambient temperature is high or there is restriction in the air flowing through the condenser, the head pressure increases. In high capacity or packaged units, the speed of the compressor is generally steady aside from those with variable speed drives. In the automobile application however, the speed of the compressor and the amount of air flowing through the condenser varies with the speed of the vehicle. So what kind of pressure (Hi side) can one expect during idling as opposed to driving speeds. It seems to me that the hi-side pressure reading is higher when idling (low compressor speed, less airflow through the condenser) that during driving speeds when both airflow and compressor speeds are much higher.

[DonSor]

Just found out the answer to may question. In my application (99 Ranger) there is a switch in the low side which controls the temperature and another switch on the high side which controls the head pressure from going too high. The clutch engages when the A/C is turned on and remains engaged unless the AC is turned off or during fast acceleration whereby the AC is temorarily disengaged to allow more of the engine horsepower to be used for propulsion.