Inspection Thought of Water Level Switch Failure in Automatic Washing Machine

There are two main reasons for the failure of water level switch in washing machine: one is that the contact of water level switch is burned out, which results in bad contact; the other is that the air chamber of water level switch leaks, and the air pressure in the air chamber can not rise, which causes the pressure switch not to act, or the air chamber leaks slowly and causes the pressure switch to reset after operation.

The main causes of air leakage in the air chamber of water level switch are: aging rupture of rubber film, aging rupture of pressure hose, blockage of gas nozzle, loosening of pressure hose and nozzle socket, etc.

Troubleshooting ideas:

(1) For the detection of bad contact fault of water level switch, the on-off condition of each contact can be judged by measuring the resistance of multimeter.

(2) For the failure of water level switch caused by leakage of air chamber, it can be repaired by the following methods.

First, check whether the pressure hose is firmly tied to the air nozzle and whether the air nozzle is blocked. The end of the pressure hose can be pulled out from the connection of the outside barrel of the washing machine and blow air into the air chamber of the water level switch through the pressure hose with the nozzle. While blowing, check whether there is air leakage between hose and air nozzle, check whether air is discharged from the outlet pipe of water level switch. If no air is discharged and there is no air leakage between hose and air nozzle, it means that the air nozzle is blocked and should be discharged in time.

(3) The judgement of whether the rubber film of the water level switch leaks or not.

When the rubber film leaks seriously, the rubber film is blown through the hose to the pressure chamber with the nozzle, and the rubber film is basically immobile. The contacts of the water level switch are not moving, and the exhaust duct is discharged with air. When the rubber film leaks not seriously, the exhaust duct is blown with the nozzle, and the corresponding contacts are moving. At this time, the washing machine will start to work normally. After washing for a period of time, the water level switch will automatically disconnect, the wave wheel will stop turning, and the washing machine can not carry out program conversion.

Whether the rubber film of the water level switch leaks or not can also be checked by a test device consisting of U-tube and pressurized air bag. The connection of the device is shown in the following figure.

When the airbag is pressed by hand, the liquid in the U-tube is pressed and the pressure is transmitted to the rubber film. If the rubber film is intact, it will bulge upward, disconnecting the COM and NC terminals of the contacts, and connecting the COM and ON terminals; if the rubber film has a leakage phenomenon and is serious, the rubber film will not bulge after pressurization, and the contacts will not undergo on-off conversion. At the same time, the multimeter is used to measure the switching status of the contacts in the process of pressurization. If the rubber film can bulge during the pressurization process, and the contacts have the above-mentioned on-off conversion, maintaining the air bag pressure state, and restoring the original on-off state between the contacts after 30 minutes, it shows that the rubber film has a slow air leakage phenomenon.

The water level switch of automatic washing machine generally adopts sealed pressure joint structure, which can not guarantee its sealing after disassembly. If the contact burns out or there is air leakage, it is usually not easy to repair, so the water level switch of the same type can only be replaced.