How to check the lock of a washing machine

UBL washing machine - this is not the most difficult device used in it, but because of it, your "home assistant" can get up dead. UBL - this is nothing more than a lock on the hatch of the washing machine, which is designed to block the hatch during the implementation of washing, rinsing and spin cycles. The lock works in automatic mode and if it breaks, it blocks the hatch or does not want to close it at all. In the article, we will tell you how to check the lock of the washing machine in different ways, in order to understand UBL broke or something else.

Lock designs

Before deciding how to check the UBL of an automatic washing machine, you need to at least roughly imagine how such a lock is arranged, and what locks are generally used to block the hatch of the “home assistant” during washing. Over the past 30 years, in automatic washing machines manufactured by different manufacturers, only two types of locks were used to lock the hatch: with a bimetallic element and electromagnetic.

Electromagnetic locks have proven to be unreliable and inefficient, since they can only reliably hold the hatch when there is electricity. Therefore, UBL based on a bimetallic plate is installed on modern washing machines. Why is such a UBL more popular and how does it work?

Everything is pretty simple. The principle of operation of the UBL washing machine with a bimetallic plate is based on the interaction of three main parts:

• thermocouple;
• bimetallic plate;
• retainer.

When the control module of the washing machine gives the UBL command to lock the hatch, voltage is applied to the thermocouple, which heats up in seconds, heating in turn the bimetallic plate. A thin and long plate from heating expands, becoming even longer, while it starts to put pressure on the latch, which immediately works and closes the lock, reliably blocking the hatch. As long as voltage is applied, the plate will be hot and the hatch door will remain locked.

If the contact of the UBL thermocouple breaks, then this thermocouple will stop heating, the plate will remain cold and the lock will not work - the hatch will remain open.

If the UBL is working properly, then when the power is turned off, the thermocouple will stop heating up, the plate will cool down, decrease in size and pull the lock to unlock the hatch. If the UBL is faulty or the corresponding triac of the control module is faulty, the power will be supplied to the lock continuously and it will remain closed until you de-energize the washing machine. This is how this device works, now let's talk about checking it.

Checking with a tester

The operation of the lock can be more or less reliably checked by a tester. It is best to use a working electronic multimeter with a large range. Before checking the hatch blocking device for the automatic washing machine with a multimeter, you will have to remove it. We will not talk again about how to remove hatch lockif you need this information, read the relevant publication on our website.

After removing the hatch lock, you need to see its diagram. The fact is that quite a few companies produce UBL with a bimetallic plate and each has its own contacts, and we need to know in advance which contact is responsible for what, in other words, where is the phase, where is the neutral, and where is the common one. You can find such a scheme on the Internet. Without a circuit, we will not be able to carry out a quality check of the hatch lock with a multimeter.

As soon as we find out about the purpose of each of the contacts of a particular lock of the washing machine, we only need to carry out a check.

• We switch the device toggle switch to resistance test mode.
• We install one probe on the neutral contact of the lock, and the other on the phase contact.
• If the device shows a three-digit number, everything is fine.
• We install probes on two contacts of the lock: neutral and general.
• If the appliance shows zero or one, the washing machine lock is defective.

If the electrician of the lock is working, but it still does not work, it is not at all necessary that the malfunction lies elsewhere, because you also need to check the mechanics of the device, suddenly a factory marriage.

Diagnostics by external signs

In some cases, it can be established with a low degree of certainty that the UBL of the washing machine is malfunctioning without even disassembling the equipment. You can diagnose a malfunction by the behavior of the washing machine itself, if you, of course, are well versed in its device and know the principle of operation of all modules. How can the washing machine behave in cases when the UBL is faulty?

1. UBL mechanics are clearly defective if if the hatch of the washing machine remains locked even after a few hours after the blackout of the "home assistant".
2. If you start the washing program, and an error code appears on the machine’s display, indicating a malfunction of the UBL.
3. You are trying to start the wash, and the UBL does not want to lock the hatch. In this case, there are two options: either it is a lock or a control module. Exactly establishing the truth will help replace UBL with a new one or check the old one with a multimeter, according to the scheme described above.

There are still ways to check the lock, but they require access to equipment that you can’t get at home, which means it’s not worth discussing.

Summing up, we note that checking the lock on the washing machine, which is responsible for blocking the hatch, is not as simple as it might seem at first glance, however, with minimal multimeter skills and an appropriate UBL scheme, it is quite possible to cope with the task. Good luck