What is the working principle of an automotive air conditioning pressure switch?

[StJune]

Here is a detailed introduction to the working principle of an automotive air conditioning pressure switch: 1. High-pressure switch working principle: The high-pressure switch is installed in the high-pressure pipeline, usually mounted on the liquid receiver-drier, and connected in series with the compressor electromagnetic clutch circuit or the condenser fan circuit. When the system pressure is too high, the high-pressure switch activates, cutting off the clutch circuit or engaging the high-speed circuit of the cooling fan to prevent further pressure increase and avoid system damage. 2. Low-pressure switch working principle: The low-pressure switch is typically installed directly in the high-pressure pipeline with a threaded connection, connected in series with the electromagnetic clutch circuit. Its structure is similar to that of a normally open high-pressure switch. When the refrigerant pressure is normal, the moving contact closes the compressor electromagnetic clutch circuit; when the refrigerant pressure discharged by the compressor is too low, the low-pressure switch opens, cutting off the electromagnetic clutch circuit, and the compressor stops running to prevent damage. 3. Dual-pressure switch working principle: New air conditioning refrigeration systems combine the high and low-pressure switches into a single unit, known as a dual-pressure switch, mounted on the liquid receiver-drier. This reduces the number of pressure switches and interfaces, thereby minimizing the possibility of refrigerant leakage. When the high-pressure refrigerant pressure is normal (between 0.423–2.75 MPa), the metal diaphragm remains in a balanced position, and both the high-pressure contacts 14, 15 and low-pressure contacts 1, 2, 6, 7 are closed. Current flows from contacts 6, 7 to high-pressure contacts 14, 15 and then to contacts 1, 2. When the refrigerant pressure drops below 0.423 MPa, the spring pressure exceeds the refrigerant pressure, causing low-pressure contacts 1, 2 and 6, 7 to open, interrupting the current and stopping the compressor. When the pressure exceeds 2.75 MPa, the refrigerant pressure continues to push the metal diaphragm upward, moving the entire assembly to the top dead center and pushing the push pin 12 to separate the high-pressure moving contact 14 from the high-pressure stationary contact 15, cutting off the clutch circuit and stopping the compressor. When the high-pressure side pressure falls below 2.17 MPa, the metal diaphragm returns to its normal position, and the compressor resumes operation. 4. Triple-pressure switch working principle: The triple-pressure switch consists of a dual-pressure switch (high-pressure and low-pressure switches) and a medium-pressure switch, offering a more compact structure. It is installed in the high-pressure pipeline. When the pressure is too high or too low, the dual-pressure switch controls the compressor to stop. When the refrigerant pressure reaches a certain intermediate value, the medium-pressure switch controls the engagement of the condenser fan circuit.