How the Door Closing Sensor (UBL) Works and How to Fix It

Any automatic washing machine is equipped with a door closing sensor. The element is connected to the lock, and together this mechanism is called the door locking device. Only after the UBL is triggered, the machine can start washing.

The door closing sensor of the washing machine sends a signal to the control module that the system is sealed, and the "brain" starts the cycle. If such information is not sent to the board, the wash does not start. Let's figure out what the UBL consists of, how, if necessary, to check and repair the mechanism.

What does the closing module consist of?

Before disassembling the door locking device, it is worth understanding what it is, what parts the mechanism consists of, how it works. Modern automatic machines are equipped with bimetallic locks-blockers. Such a module is very reliable - it will not allow the door to be opened during washing. So, the door lock of the washing machine includes:

• Thermoelement,
• Fixing tongue,
• Bimetallic plate.

The operating principle of the door locking module is as follows:

• The control unit supplies current to the lock's thermal element,
• The thermoelement heats up in 1-3 seconds,
• The charge is transferred to the bimetallic plate,
• The plate changes in size and exerts pressure on the retainer,
• The "tongue" falls out and remains in a special recess.

The hatch opens in the same way, only all actions are performed in reverse order. The bimetallic plate, when the current supply stops, changes shape, the lock "comes out" of the groove and "stands" in its place. The door lock is removed.

It should be understood that on most models of washing machines the UBL is activated only 1-3 minutes after the end of the cycle. Therefore, do not try to forcefully open the door immediately. You need to wait until the plate cools down, and the control module makes sure that there is definitely no water left in the tank.

If the hatch does not open after 10-20 minutes, most likely, there was a failure in the mechanism. We will tell you below why the blocker may break, how to check and repair it. The blocking device is located on the front wall of the housing, to the right of the drum door. Its location is indicated by a small rectangle protruding slightly outward. This is the groove where the "tongue" of the lock enters.

What causes breakdowns?

The door closing sensor of a washing machine usually breaks down for two reasons. Most often, the malfunction of the lock is caused by banal wear of the mechanism parts due to long-term operation of the machine. So, time after time, when heated, the plate deteriorates, and after a few years the fixation weakens to a minimum. If this is the case, repairing the lock will be inappropriate, it is better to remove the old one and install a new UBL.

In addition, problems with the machine's electronics may cause the blocking device to malfunction. This may be because:

• Voltage surges in the electrical network “break through” the thermal element of the lock, it stops heating up and transmitting charge to the plate and hook,
• The thyristor on the board, responsible for the operation of the blocker, closes, as a result of which current is constantly supplied to the ubl, so the door lock is not removed.

Mechanical reasons also lead to malfunction of the UBL. The door may not open if there is sagging, or the hinges on which it is fixed are deformed. In addition, the "tongue" in the lock itself may break. To prevent such problems, it is important not to hang things on the hatch, do not allow children to ride on it.

Understanding the operating principle and the structure of the locking device, you can independently determine the cause of the breakdown. We will tell you how to diagnose the mechanism yourself. Having found the problem, it remains to fix it and continue washing.

How to test a part?

It is usually very easy to understand that the door locking device is faulty. With such a problem, the washing machine clearly indicates a malfunction. Among the main "symptoms":

• The hatch does not open, even after 1-2 hours from the end of washing,
• The display shows the corresponding error code or the led of the start/pause button on the dashboard flashes 17 times (other indicators may also light up, depending on the model of the washing machine),
• The door does not open even when the washing machine is disconnected from the electrical network,
• After starting the wash, the lock does not work, the machine does not start the cycle.

How to check the door closing sensor of the washing machine for operability? You can perform diagnostics using a multimeter. First, you should look at the instructions and study the electrical circuit of the washing machine. This will help you understand where the phase is, as well as the neutral and common contacts of the UBL. After that, you can begin to dismantle the blocker. You need to do the following:

• Turn off the power to the machine,
• Close the valve responsible for the water supply,
• Disconnect the equipment from communications,
• Open the hatch,
• Unscrew the bolts securing the UBL,
• Unscrew a couple of screws holding the top cover of the washing machine,
• Push the panel towards you and remove it,
• Slide your hand down towards the lock (it is located to the right of the cuff),
• Unhook the wires connected to the lock,
• Remove the device from the case.

Afterwards, you can “arm yourself” with a multimeter, switch it to the resistance determination mode and place the tester probes against the neutral contact and phase of the lock. The display should show a three-digit number. If the value does not match, replace the UBL. At the next stage of testing, you need to attach the wires to the common contact and phase. Using a screwdriver, you need to move the “tongue” of the lock to the working position and connect the device to the network. A working blocker will click; a broken one will be “silent”.

If diagnostics do not reveal any problems with the lock, inspect the hinges. They may be deformed, which is why the door sags. Mechanical damage to the mechanism's "tongue" may also be the reason for the machine's reluctance to lock the hatch. Be sure to check this guess as well.

How to understand that the closing sensor is broken?

Knowing the operating principle of the door lock, it will be easy for the user to guess about its malfunction. The behavior of the automatic machine will immediately reveal the problem. As already mentioned, you can suspect a malfunction with the locking mechanism if:

• The door lock is not removed long after the wash cycle is completed,
• The machine displays a fault code corresponding to this problem,
• The brain does not lock the door after selecting the desired mode and starting the cycle.

An alarm bell will be the need to press on the machine door every time you start washing to activate the UBL. This indicates a weakening of the fixation - it is better to check it immediately and, if necessary, replace the lock.