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Vehicle: Rui euro GL car, equipped with 1.4L engine, manual transmission. Driving mileage: 1000km. Failure phenomenon: users reflect the use of the car after the purchase of normal air conditioning, the recent weather is hot, there is a different noise in the engine cabin, and air conditioning hot air, and sometimes the engine flameout. Fault diagnosis: first of all, test with the user, failure as described by the user. Reading detector, no fault code storage, read the data flow discovery, when the fault occurs, the air conditioning switch oN and oFF fast conversion, compressor shutdown, the fan high-speed display 0N. The possible reasons for this failure are: 1. air conditioning pressure sensor damage. 2. the cooling fan is damaged. 3. overcharge the refrigerant. 4. condenser clogging or heat sink clearance is blocked by impurities. 5. the internal blockage in the air conditioning refrigeration loop. 6. line fault and so on. When the vehicle stopped, the pressure of the air conditioning system was measured, and the pressure value was too high. The high pressure reached 23kg / cm at idle speed. Check the fan, the fan works normally, pull off the fan resistance, and the fan is still rotating, indicating that the fan is running at high speed. Check that the water tank and the condenser are dirty. After cleaning, the pressure is still high. The refrigerant was recovered and an excess of refrigerant was found. Troubleshooting: add the refrigerant according to the prescribed amount. Test the car, troubleshooting. Fault summary: as the weather overheated, the refrigerant added too much, the air conditioning pressure was too high. In order to ensure the safety of the air conditioning refrigeration system, when the pressure of the air-conditioning refrigeration system exceeded 32 2kg / cm2, the air conditioning pressure sensor gave the engine control unit high pressure information, the engine controlled the single unit to cut the compressor, causing the air conditioning incool. Because the pressure is too high, the engine load is too large, resulting in engine sometimes flameout, compressor clutch slip abnormal noise.