Fault phenomenon: a Toyota crown (CROWN) MS112 car air conditioning, in the early stages of the refrigeration system, the cooling situation is also basically normal; to the evaporator mouth blowing the wind is cooler (about 16-18 ℃), the compressor automatically stop. After a period of time, the compressor is automatically connected to the operation, and re-cooling. So reciprocating, the temperature inside the car can only be maintained at 16-18 ℃, can not continue to decline.
    Troubleshooting: According to the above fault phenomenon, can be initially judged as the expansion valve in the refrigeration system "ice plug". Because of the "ice plug", the high pressure liquid refrigerant on the left side of the expansion valve can not pass through the ball valve and evaporate into low pressure, low temperature vaporized refrigerant (because the ball valve has been "ice plug" blocked, no channel). In this way, the evaporator can not get enough supercooled steam, of course, there is no cold air sent out. When the compressor stops for some time, the expansion valve at the "ice plug" is thawed, the channel is opened, and restore the cooling. "Ice plug", the compressor automatically stop the rotation because the "ice plug" after the low pressure side of the pressure drop, so that low-voltage switch to work.
    In order to confirm if the expansion valve is "ice plug" as soon as possible, use the following inspection method: with a small cotton ball dipped in alcohol, lit, and then heat the valve for several minutes. After heating, the low pressure side of the pressure rise, the compressor to resume work. This shows that the expansion valve does have "ice plug".
    To exclude the "ice plug", it is necessary to exclude the system of water. The method is: the system will be disintegrated, the parts were cleaned, and then dry and dry, and replace a new liquid storage a filter, and then according to strict operating procedures installed. After this treatment, the fault is excluded.
    Failure analysis: "ice plug" is due to air conditioning system in the water into the produce. Such as improper maintenance operations, vacuum is not complete, as well as refrigerant or refrigerated oil in the water content of the high side, will make water into the system. In order to remove moisture, the system is equipped with a liquid storage drying filter, where the desiccant can absorb a small amount of water into the system. However, if the water into the system too much, it will make the desiccant failure, resulting in "ice plug."