How is the AC Compressor designed?

Does it cycle on/off on a set frequency, or does it kick on as needed based on the cabin temp?

 

ac compressor kicks on as pressure changes in the system. you have a high and low pressure switches in the system to kick it on and off.
what is the issue?

 

No issue. Just curious if setting the blower to HI causes the compressor to cycle more often, which would reduce MPG even more.

It sounds like this would be the case...

 

the blower motor is a separate parasitic drain on mileage. ie electrical system.

 

There is a Thermistor at the evaporator coil that controls the compressor clutch. It is to prevent the coil from freezing.