How does the pressure switch of a washing machine work?

The water level sensor helps the control module monitor the fullness of the washing machine tank. Without this small part, the machine simply will not complete the wash; the cycle will “freeze” before it even starts. We will analyze the device of the washing machine pressure switch and tell you how you can diagnose it at home. Let us describe the principle of operation of the element.

What is this detail?

Modern automatic machines have many components and components. Each part performs a specific function. The pressure switch monitors the water level in the tank. The sensor measures how much liquid is in the “centrifuge”, focusing on the pressure in the tube.

The complexity of the water level sensor directly depends on the number of washing modes stored in the machine’s “memory”.

The relay is made in the form of a disk. Inside the pressure switch there is an air chamber with a diaphragm, a magnetic core and a tube. Sensors can be of simple or complex types, differing in the sensitivity of the membrane and the stroke of the rod.

The pressure switch from one machine does not always fit another washing machine. Therefore, if the factory sensor breaks down and requires replacement, be sure to look for and buy an analogue, focusing on the model and serial number of the machine. The “shell” of the pressure switch is made of high quality plastic. Externally, the relay resembles a washer. The sensor is assembled from the following components:

• plastic “shell” (body);
• coil;
• membrane. She is able to change shape under pressure and press a switch;
• magnetic core (plays the role of a switch);
• wires.

Depending on the model of the automatic machine, the pressure switch needs to be looked for in different places.The water level sensor is installed:

• under the top panel of the case (on most front-facing cameras);
• from below, under the tank (in “verticals”);
• at the back of the body, just below the tank. This arrangement is typical for SMAs with plastic drums.

Now it’s clear how the pressure switch works and in which part of the washing machine to look for it. We will also analyze the principle of operation of the level sensor. Let's tell you what its role is in an automatic machine.

How does the sensor work?

A pressure switch is provided in any automatic machine. It is necessary to control the water level. The sensor sends a signal to the “brain” of the washing machine, notifying the controller about the degree of fullness of the tank. This information is used by the module to control the wash.

As the SMA tank fills, the pressure in the tube and air chamber of the pressure switch increases.

The sensor membrane is very sensitive. Under pressure, the rod rises and presses on the plate with the spring. When the water in the tank reaches the desired level, the circuit closes. The pressure switch notifies the module that there is enough water, and the controller starts the next “step” of the wash. At the draining stage, the pressure in the pressure switch tube decreases, the rod begins to descend along with the plate. The electrical circuit is broken.

Typical problems

You can understand that the water level sensor is not functioning correctly by a number of signs. Firstly, this is the error code displayed on the machine display. If the self-diagnosis system does not detect a breakdown, a malfunction of the pressure switch should be suspected if:

• repeating the cycle. When the sensor does not monitor the water level, washing does not work correctly. In this case, replacing the pressure switch will help;
• lack of water supply. There may be a situation where the cycle has started, but the machine does not fill.Usually the reason for this is the pressure switch contact sticking in the “full” position;
• continuous supply of water. Sometimes a faulty pressure switch constantly signals that the tank is empty, while the liquid reaches the upper mark. In this case, the drain automatically starts, and the machine continues to fill. The process occurs in a circle;
• incomplete drainage of water from the tank. Of course, this is not a clear sign of a faulty pressure switch, but it is quite possible that it is because of a broken level sensor that some of the liquid remains in the drum;
• deterioration in wash quality. Clothes may not be washed if there is not enough water in the tank. This happens when the relay is not adjusted correctly. To correct the situation, just adjust the pressure switch by tightening the adjusting screw;
• burning smell coming from the machine. In this situation, the washing program still starts when there is no water in the tank, but the relay indicates that it is full. The heating element heats up, and since there is no liquid inside, the washing machine begins to smell burnt. It is important to de-energize the equipment as quickly as possible to stop its operation.

Having noticed one or more “symptoms”, it is better not to “torture” the machine further, but to check the pressure switch. It is not always necessary to change the water level sensor; sometimes it is enough to clean and adjust it. Let's figure out how to diagnose an element.

Checking and adjusting the sensor

Before you disassemble the washing machine body with your own hands, check whether the machine is under warranty. If the free service has not yet expired, it is better to invite a specialist to diagnose it. If you carry out unauthorized repairs, you can forget about warranty service.

If the warranty on the device has long expired, you can start self-diagnosis.You should proceed like this:

• unplug the machine's power cord from the network;
• close the shut-off valve responsible for the water supply;
• unscrew a pair of screws holding the top panel of the machine;
• remove the “cover” of the washer body;
• find the pressure switch;
• Unscrew the screw fixing the relay in the housing and remove the connector;
• loosen the clamp and remove the pressure switch from the machine.

Before changing or adjusting the device, you should check that it is working properly. To do this, you will have to prepare a short rubber tube, the same as on the pressure switch. Having pulled out the water level sensor, connect the prepared tube to it. Next, blow into it - if the pressure switch is working, two or three characteristic clicks should be heard. Silence will indicate that the contacts are not actuating, therefore the relay is faulty.

Next, inspect the pressure switch and make sure there is no damage to it. Also check the hose for blockages - if it is clogged, blow it out or rinse it under running warm water.

You can check the water level sensor using a multimeter.

Hardware testing of the pressure switch is considered more accurate. To perform diagnostics, switch the multimeter to ohmmeter mode and attach the probes of the device to the relay contacts. Be sure to create pressure in the tube for the contacts to work. If the numbers on the tester screen do not change when the contacts are activated, you will have to replace the pressure switch. When everything is in order, you don’t have to purchase a new sensor, but simply adjust the existing one.

The pressure switch is adjusted manually. The adjustment will help if too little water gets into the machine when washing. The volume of liquid can be made smaller or larger - to do this, you need to set the relay response force. Before starting the procedure, be sure to turn off the power to the equipment.

Remove the top cover of the machine, find the pressure switch and reset the connector. The level sensor has 3 adjusting bolts; one of them will have to be tightened during the process. The screw with which the adjustment is made is usually located in the central part.

It is necessary to adjust the pressure switch when the washing machine tank is empty.

You can tighten the screw using a Phillips screwdriver or an asterisk. The procedure is carried out in stages - it is important to evaluate the intermediate results of setting up the sensor. So, you need to turn the bolt half a turn, then assemble the machine and run the test cycle with an empty drum. When the results are not satisfactory, you still need to turn the screw.

It is necessary to set up a pressure switch with at least minimal basic theoretical knowledge. If you have absolutely no idea how the level sensor works, it is better to entrust the work to a specialist. A specialist will adjust the relay correctly.

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