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10/10/2020

Air conditioning failure case sharing

Repair shop consultation, air conditioning high pressure pressure is too low, check compressor damage, air conditioning pipeline has metal debris, replace compressor, I told him that in addition to replacing compressor, condenser must be replaced. And clean the pipeline thoroughly.


The car is coming. Let me clean the pipes. After connecting the equipment and cleaning the pipeline, evacuate, add oil and charge refrigerant. The engine found that the pressure is not correct. The high pressure is 5bar, and the low pressure is lower than 0bar. It is obvious that the system is blocked.


The compressor is blocked, and the system is blocked again. Remove the condenser, remove the side dryer bottle plug of the condenser, the filter screen is blocked by desiccant, and all the small particles of the desiccant leak out. The condenser must be replaced.





Re clean the air conditioning pipeline, including evaporation tank, replace condenser, and troubleshooting.


Summary:


The compressor of air conditioning system is an important component. There is no piston ring between the compressor piston and the cylinder liner, which is completely sealed by clearance. Therefore, even tiny particles can lead to excessive wear of the compressor. For the compressor damaged by piston and cylinder liner wear, there will be debris after piston wear in the whole air conditioning system. If these debris cannot be cleaned, the new compressor will be scrapped.


The main function of the condenser in the system is that the refrigerant changes from liquid state to gas state, and the other function is to filter impurities. Therefore, the condenser must be replaced for vehicles with damaged compressor.



Now the air conditioning cleaning equipment can use refrigerant to clean the whole air conditioning system, and filter out all the impurities in the system. This way has no harm to the air conditioning system.


BMW air conditioner is not cool


Model: BMW 730, F02 chassis


Trouble: the air conditioner doesn't cool after a while


When the air conditioner is not cool, check that the system is not short of refrigerant and the pressure is abnormal. High pressure 10 bar, low pressure 5 bar, the high pressure of the fuel valve does not increase, and the low pressure does not change.


This phenomenon seems that the compressor compression capacity is not enough, the pressure is too low. Replace the compressor, the fault still remains after driving for a period of time


Do the basic inspection first. When the air conditioner is turned on, the electromagnetic clutch of the compressor is closed, and the variable displacement solenoid valve has more than 11 volts of voltage. The control of the air conditioner is OK. And replaced a compressor, run for a week, and not cool, or high pressure low pressure high. Clean the air conditioning system again, add refrigerant, start the car, turn on the air conditioner, the fault is still the same.


When cleaning the pipeline, it was found that the resistance of the low-pressure pipe was large. The rubber tube of the low-pressure pipe was cut open, and the inner layer of the rubber tube was peeling, which blocked the pipeline during the refrigeration cycle. However, the low-pressure inspection port of the air-conditioner was in the front of the hose, so the vacuum state of the low-pressure system inside the compressor could not be displayed. On the contrary, because the pressure on the high-pressure side acted on the low-pressure side through the expansion valve, and it was in the inspection port The pressure is too high. This led us to misjudge the compressor failure.


Summary:


The maintenance pressure of the air conditioning system can be used as the main reference data, but it is not the only one. The circulation of the air conditioning system and the temperature of various parts are the main basis for judging the air conditioning failure. Air conditioner is not cool in Jiefang xindawei


Model: Jiefang xindawei


Fault: the air conditioner is not cool


The car's air conditioner is a rear mounted air conditioning system with R12 refrigerant. When I repaired, the compressor had been replaced and R134a refrigerant was added. First of all, the two refrigerants can not be mixed. The refrigerants are replaced again. The engine still doesn't work. The high pressure pressure is 11bar, the low pressure pressure is lower than 1bar, and the low pressure is too low.


This is a system blockage. Remove the pipeline and condenser again and check that they are normal and not blocked. When I charged the refrigerant again, the fault was still the same. At this time, I directly removed the low-pressure pipe of the expansion valve at the evaporation tank. There was no refrigerant discharged from the expansion valve, and the expansion valve was stuck.


Replace the expansion valve. Before loading, use compressed air to test whether it can be opened, but it can't be opened. Adjust the spring pressure of the expansion valve, and the expansion valve can be opened normally. If it is loaded and tested again, it still doesn't circulate. Gently tap the expansion valve with a wrench for a few times, and the circulation suddenly opens. The high and low pressure are normal, and the air conditioning refrigeration is also good.


Summary:


It's a cyclical problem. The quality of the added air conditioner parts is too poor. The expansion valve is rarely broken when repairing the air conditioner. Therefore, the expansion valve is rarely considered, and the result is still a detour. The compressor of the original car is not broken.