In an automatic washing machine, each part is responsible for a specific job – for example, a special UBL device closes the door. This electronic interlock locks the door when closed by sending a signal to the control module. When the locking device is activated, the wash begins.
We will consider the reasons for the breakdown of the locking device, as well as options for checking it.
The principle of operation and types of blocking
Before you check the lock in the washing machine, you need to understand how this device works. Often, in modern cars, manufacturers use two types of locks:
Electromagnetic. This blocker is used less and less. The inconvenience of its use is that it works as long as there is a supply of electricity. If it is disabled, you will not be able to open the hatch.
Bimetallic. The device and principle of operation of the lock on the hatch door are quite simple: electricity is supplied to a thermal element, which heats up due to this. At the same time, it heats the bimetal plates, due to which they bend, putting pressure on the lever. The latter works and closes the door.
Such thermal locks with bimetallic plates are considered the most effective.
There is a delay when the door is unlocked. For what? Until the water is completely drained and all parts of the machine stop moving, the door should not be opened for safety reasons.
Another plus of thermal locks is that they can be opened in case of a power outage.
Why UBL fails
You have already understood how the UBL of a washing machine works and what are the advantages of using it. Why does the lock break? Here are the main reasons for the failure:
- Long-term use contributes to the wear of bimetallic plates. As a result of constant deformation, the plates lose their functional qualities.
- Due to a short circuit, the device also fails.
As long as the device is powered, it works. Therefore, if your washer stopped, but the door did not unlock, do not rush to blame the locking device. Most likely, the triac broke down on the electronic board, which is responsible for the operation of the UBL. Power is supplied continuously, so the door does not open.
Self-checking the CMA lock
There are a number of external signs by which the user may assume a lock malfunction:
- The CM is disabled, but the door remains closed. The reason lies in the blocking device or in the main module.
- When you start the program, washing does not start, the hatch remains open.
- The washer issues a fault code indicating a broken lock.
To understand if the lock is broken or something else, you need to know how to check the UBL in the washing machine with a tester.
You will need to remove the device from the car:
- Unlock SMA from sets.
- Open the door.
- Bend the cuff of the hatch and remove its collar.
- Pulling the cuff from the side, you will see the lock.
- Unscrew the two screws securing the lock.
- Unclip all connectors and remove the blocker.
Now that you have the UBL in your hands, you can start checking the washing machine lock. To use a multimeter, you need a lock circuit. This is necessary to determine the location of the common and neutral contacts.
At home, you can only check the thermocouple that heats the plates.
- Set the tester to resistance measurement mode.
- Attach its probes to the neutral and phase contacts.
- The lock is working if a three-digit number appears on the screen.
- Move the tentacles of the multimeter to the neutral – common contacts.
- The device is faulty if the display shows 1 or 0.
Once you figure out how to properly test your washer’s hatch lock, you can install a new lock. Proceed like this:
- Connect the wires to a working device.
- Get it behind the wall of the case, install it in the hole for the lock.
- Tighten the fastening screws.
- Reinstall the cuff clamp.
Checking the UBL in the washing machine is not a difficult task, you can do it yourself. Of course, if the lock is broken, the door will not close, so the wash will not start for your safety.
Installing a new blocker is not difficult for a beginner, the main thing is the sequence of actions.