company news about Basic Diagnosis of Automobile Air Conditioning Failure

Accurate diagnosis of automotive air conditioning refrigeration systems, especially fault diagnosis, is performed by reading the manifold pressure gauge. The specific reading of the manifold pressure gauge is associated with a specific problem, and multiple problems may result in the same specific reading. During normal operation of the refrigeration system, the refrigerant becomes gaseous as air passes over the evaporator surface, removing heat. Therefore, the low-pressure side pressure reading is related to the liquid refrigerant temperature. Since the system releases heat when outside air passes through the condenser, the refrigerant becomes liquid. Therefore, the high-pressure side pressure gauge reading is related to the gaseous refrigerant temperature.

During use, it is necessary to frequently check the manifold pressure gauge to ensure that the pointers of the high and low pressure gauges remain at the "zero" position. You can use a flat-blade screwdriver to calibrate the pointers so that they point to the "zero" position.

Connect the manifold pressure gauge, idle the engine, and run the air conditioning system for approximately 15 minutes. Once the system is operating normally and a steady stream of cool air is flowing out of the air outlet, observe the gauge pressure. When the refrigeration system is operating normally, the standard pressure is approximately 1.5-2.5 bar on the low-pressure side and approximately 15-20 bar on the high-pressure side.

Fault phenomenon: As shown in the figure below, the pressure on the low-pressure side and the pressure on the high-pressure side are both lower than normal, and it can be felt that the air outlet temperature is not low enough and the outlet air (cold air) is not cold enough.

Cause of failure: Insufficient refrigerant, insufficient refrigerant flow or refrigerant leakage

Fault phenomenon: The pressure on the low-pressure side is higher than normal, and the pressure on the high-pressure side is lower than normal; the compressor makes noise; the temperature of the air outlet feels high; when touching the high-pressure side pipeline, the pipeline does not feel hot.

Cause of failure: There is a mechanical failure in the compressor; there is a blockage between the compressor intake pipe and the pressure gauge or the liquid storage dryer

Fault phenomenon: The pressure on the low-pressure side is lower than normal, even tending to vacuum, and the pressure on the high-pressure side is lower than normal; the air outlet temperature is not low enough, only slightly cool, but the low-pressure side pipeline may have been frosted.

Cause of failure: The throttle tube (or expansion valve) is blocked by debris.

Fault phenomenon: The pressure on both the low-pressure side and the high-pressure side are lower than normal; the air outlet temperature is not low enough, only slightly cool; there are a large number of water droplets or frost after the blockage point on the high-pressure end.

Fault phenomenon: The pressure on the low-pressure side and the high-pressure side are both higher than normal; the temperature at the air outlet is not low enough, only slightly cool.

Cause of failure: After the system components are replaced or repaired, the vacuum is not fully drawn, resulting in residual air in the system; the components are poorly sealed, causing air to enter the refrigeration system.

Fault phenomenon: The pressure on the low-pressure side is lower than normal, even approaching vacuum, while the pressure on the high-pressure side is normal; the air outlet temperature is unstable, sometimes cooler, and sometimes only slightly cool, but the low-pressure side pipeline may have been frosted.

Cause of failure: There is too much water in the system, which may cause ice to form inside the throttle tube or expansion valve.