When a Cherokee off-road vehicle is used in summer, the cooling effect is not good. The faster the speed, the worse the refrigeration effect. Generally speaking, when the car uses air conditioning in situ, the effect of refrigeration is poor. In the course of driving, the cooling effect of air conditioning will be improved. The reason is that the car has enhanced the cooling performance of the condenser in the front of the car. During the maintenance, the air conditioning manifold pressure meter (combined double table) is connected to the corresponding interface of the high and low pressure tube of the air conditioning system, and then the switch is opened. It is observed that the static pressure value of the refrigerant in the air conditioning system (when the engine is not working) is 0.6MPa in the normal range. After starting the engine, the air conditioning control switch is pushed to the position of MAX (maximum refrigeration state). The air conditioning compressor works. There is no bubble in the observation hole above the liquid storage dryer tank. At this time, the high pressure meter indicates the value, the high pressure side is 1.45MPa, and the low voltage side indicates 0.125MPa. All instructions indicate that the refrigerant in the air-conditioning system is adequate, and the working pressure at high and low pressure side is normal. The touch of the low-pressure tube feels cold, indicating that the car's air conditioning system works normally, but the cooling effect is poor. Then check the cooling air blow out of the central outlet of the instrument platform, basically normal, but the air volume is not large. Because of the small air volume, the temperature of the cab is reduced slowly and the cooling effect is not good. According to the fault phenomenon, it is preliminarily judged that the blower may be faulty or the blade of the air conditioner evaporator is fouled. After checking the wind speed of each block of the blower, the speed change resistance is good, and the dirt on the evaporator blade is not much. Basically, there is no blockage. Inspection found that the air outlet of the central outlet of the instrument platform was driven and opened by the vacuum action cylinder. When the air conditioning control switch is placed in the MAX gear, the central outlet of the instrument panel should be fully opened, while the defrosting outlet should be closed, and the outlet of the floor should also be closed. In the inspection, the air conditioning control switches are placed in the normal refrigerating state, the double air inlet air supply, the ventilation state, the hot air state and the defrosting state. The actual situation shows that the vents outside the central outlet are converted to normal, which indicates that the vacuum system includes the vacuum source, the vacuum pipeline, the vacuum switch and the floor, Defrosting, internal and external circulation and other throttle actuated vacuum action cylinders are all normal. Failure may occur in the central air outlet of the instrument console to drive the vacuum action cylinder. In the lower part of the dashboard, the air conditioning control switch is placed in the MAX gear. When working in the air conditioning refrigeration system, the vacuum tube is tested on the vacuum action cylinder driven by the outlet of the dashboard, and the vacuum suction is proved in the vacuum tube. When the vacuum tube is inserted into the vacuum action cylinder, the vacuum action cylinder does not move, indicating that the vacuum action cylinder has been damaged. Although the air conditioning refrigeration system of the car has sufficient refrigerant and normal refrigerating capacity, the central air outlet of the dashboard can not be opened when the air conditioning control switch is placed in the MAX gear, while the air conditioning control switch is placed in the central air outlet of the dashboard of the dashboard, and the other outlet is closed and accumulates at the cooling place of the air conditioner. Because of the small wind speed and air volume, it can not be transported to the cab to complete the cooling function. The accumulated cold energy causes the temperature switch to open for a long time and the closing time is short. Of course, under the control of the temperature switch, the air conditioning compressor is also a short working time and a long time. In this case, it is self-evident that the cooling effect in the driving room is bad. In the passenger car, the working time of the air conditioner compressor is shorter because of the increase of the cooling efficiency of the condenser in the front of the car. After changing the 1 same type of driving vacuum action cylinder, when working in the air conditioning system, the blower switch is placed in the high speed gear and the outlet of the dashboard is completely opened. The cooling air blowing out is not only cool but also the air volume is large, the cooling effect in the driving room is good, and the cooling effect of the air conditioning in the car is better and the fault row is better. Except.