High And Low Pressure Sides

High pressure side are the condenser, receiver and restrictor or expansion valve to separate the high and low pressure liquid ends.

High pressure results from the restrictor or expansion valve forming a constriction and causing the refrigerant to accumulate, thus leading to an increase in pressure and temperature.

Excess pressure results if too much refrigerant or refrigerant oil is used, the condenser is contaminated, the radiator fan is malfunctioning, the system is blocked or if there is moisture in the refrigerant circuit (the restrictor or expansion valve freezes).

Low pressure side are the evaporator, reservoir, evaporator temperature sensor and compressor to separate high and low pressure gas ends.

A drop in system pressure can occur due to loss of refrigerant, restrictor or expansion valve (restriction not given), A/C compressor malfunction or iced evaporator.