air conditioning pressure switch

Before, we have introduced the composition and working principle of each system of the car air conditioner, and know the various states of the refrigerant in the air conditioning pipeline.
For example, after passing through the expansion valve, the low-temperature and low-pressure mist refrigerant exchanges heat in the air-conditioning evaporator. The refrigerant becomes a low-temperature and low-pressure gas, and then passes through the air-conditioning compressor into a high-temperature and high-pressure gas.This pressure monitoring is recognized by the air-conditioning pressure switch.But what is the air conditioner pressure switch? What is the working principle of the air conditioner pressure switch?

The role of air conditioning pressure switch

The air-conditioning pressure switch is installed in the air-conditioning condensing line, mainly to detect the pressure of the refrigerant in the air-conditioning line.Air conditioning pressure switches are sometimes called two-state pressure switches, or three-state pressure switches.

Two-state pressure means that it can detect high pressure and low pressure, while a three-state pressure switch can also detect medium pressure.At present, there are basically three-state switches in the market. The high pressure and low pressure switches are generally connected in series in the circuit, which are normally closed switches, and the medium pressure switches are connected in parallel with the high and low pressure switches, which are normally open switches.

The following figure is a schematic diagram of the interface definition of the air conditioner pressure switch,
Combining the above analysis, A-C is the medium voltage circuit, and B-D is the high and low voltage circuit.It is worth reminding that the air-conditioning medium-voltage circuit has a larger spacing than the high-low pressure circuit.
(Please pay attention to this sentence, it is often used in actual air conditioning system maintenance)

Working principle of air conditioner pressure switch

The function of the air-conditioning pressure switch is to monitor the pressure of the refrigerant in the air-conditioning pipeline and feed it back to the air-conditioning controller or ECU.

The function of the high and low pressure switch is that when the pressure of the refrigerant in the pipeline is too high, the high pressure switch is turned off, and the signal is fed back to the engine ECU, and the ECU controls the air conditioner compressor to stop working to prevent excessive pressure from causing pipe burst;When the refrigerant pressure is too low, the low-pressure switch is turned off. After receiving this signal, the ECU knows that the refrigerant is insufficient and the compressor does not work;

The function of the medium pressure switch is when the pressure in the refrigerant tube is greater than its set value, the switch is closed. After the ECU receives this signal, it sends a low signal of the high-speed electronic fan relay, and the high-speed electronic fan works.(Generally, vehicles with electronic fans need to be equipped with a medium voltage switch)

The working principle diagram of the air-conditioning pressure switch is as follows. With reference to the figure above, it is easy to interpret the working principle of the air-conditioning pressure switch by referring to the function of the high and low pressure and medium pressure switch circuits of the air conditioner.

The air-conditioning pressure switch has developed from the initial two-state pressure switch to the three-state pressure switch. However, with the development of technology, air-conditioning pressure sensors are now being used on high-end models.
the ECU can know the constant pressure in the air-conditioning refrigerant pipeline to perform more effective control.