After the replacement of pressure control valve air conditioning work normally

Symptoms: a Shanghai Buick sedan, driving process, the air conditioning air outlet air capacity gradually reduced to disappear, but after 6-7 minutes, returned to normal. Failure Analysis: Buick car equipped with a variable displacement compressor, the level of its refrigeration depends on the level of the air-conditioning pump, according to the pressure changes automatically adjust the temperature, air-conditioning control system does not collect the evaporator outlet temperature signal. In the whole process of refrigeration, air conditioning pump is always running. The adjustment of the cooling intensity depends entirely on the pressure control valve installed inside the air conditioning pump to control. Pressure drops if pressure regulator is at low pressure. If the pressure on the high pressure side rises to a certain extent, the pressure regulating valve shortens the effective stroke of the five small pistons in the air conditioning pump, which will reduce the cooling intensity of the air conditioning pump. When the high-pressure end of the pressure drops to a certain extent, the low-pressure end of the pressure rise to a certain extent, the pressure regulating valve is to increase the piston effective stroke to improve the cooling intensity. The key to this process is the spring force of the spring inside the pressure regulator. If the elastic force of the spring increases, it will cause the pressure pulling point to move upward, resulting in excessive cooling intensity, resulting in the frosting of the outer wall of the evaporator and the air-conditioning outlet without wind. When the outer wall of the evaporator after the dissolution of the system has returned to normal. Failure reason: Buick car air conditioning system to add refrigerant for the R134a. When the system mixed with R12, will result in increased system cooling capacity. After working in this state for a period of time, the temperature is too low will increase the spring coefficient of the pressure regulating valve, the system failure. Remedy: Empty the system of refrigerant, replace the pressure regulator, filled with pure R134a refrigerant, troubleshooting.