A/C Pressure Switch
A safety sensor that monitors pressure in the A/C lines to disable the compressor if pressure is too high or low.
The A/C pressure switch is a safety sensor that monitors the pressure of the refrigerant inside the air conditioning lines. Most systems feature a low-pressure switch on the suction line and a high-pressure switch on the discharge line, or a single combined sensor.
The low-pressure switch protects the A/C compressor by shutting it off if refrigerant pressure drops below a safe level, which usually indicates a leak. Because the compressor relies on lubricant carried by the refrigerant, running it dry would quickly destroy it.
The high-pressure switch protects the system by disabling the compressor if line pressures rise to dangerous levels, which could happen if the condenser fan fails or the system is overcharged, preventing lines or seals from bursting.
A faulty pressure switch can prevent the A/C compressor from engaging even if the system has the correct refrigerant charge. Diagnosing switch issues involves using A/C gauges to verify system pressures and testing the switch electrical continuity.