Any modern electromechanical equipment is equipped with special devices that regulate its operation and protect it from overloads. In refrigerators of any manufacturer, such a device is a start-up relay. Thermal relays play an important role in refrigeration units. Its malfunction can lead to incorrect cooling mode and loss of equipment functionality.
Start-up relay - top view
Start relay connection diagram
This device is necessary to start a single-phase asynchronous compressor motor. The motor stator includes two windings - starting and working. The first serves only to create starting torque and start the compressor. The second winding is needed to maintain the rotor in working condition by continuously supplying alternating current to it.
Important! To regulate the process of supplying and turning off power to the starting and operating windings of the electric motor, as well as for the overload protection function, a starting protection relay is provided.
Inductive closing mechanism
The relay connection diagram is not complicated. Conditionally “zero” and “phase” power is supplied to the input of the device, and at the output “phase” is divided into two lines. The first line is connected to the working winding of the electric motor, and the second line is connected to the starting winding through the starting contact.
In relays of old and modern refrigerators, current is supplied to the working winding through a spring with high resistance, and then through a connection with a bimetallic jumper. With a strong increase in current in the circuit (motor jamming, short circuit between turns, and other breakdowns), the spring in contact with the jumper heats up, which changes its shape under the influence of temperature, thereby opening the contact and turning off the compressor.
Inductive circuit circuit
In this circuit, a coil (K1) is used to start the electric motor, which is connected in series with the working winding. Applying voltage while the motor rotor is stationary provokes an increase in current in the coil with the formation of a magnetic field that attracts a movable core that closes the starting contact. After the rotor picks up speed, the current in the circuit decreases, the magnetic field in the solenoid decreases, and the starting contact opens by gravity or a compensating spring.
PTC switching mechanism
Modern household refrigerators use a start-up relay with a built-in posistor (a resistor that increases resistance as the temperature rises). The circuit of this device (Fig. 2) is similar to an induction relay, only instead of a coil, a posistor connected to the starting circuit is used to close and open the starting contact.
When power is supplied to the compressor, the temperature of the resistor is low and it passes current to the starting winding. Since the resistor initially has resistance, it heats up and opens the circuit of the starting winding of the engine. The cycle is repeated after the thermostat is triggered and the refrigerator is then turned on again.
PTC switching mechanism
How to test the refrigerator start relay
It is not uncommon for a refrigerator to suddenly break down. The cause of the breakdown can be many factors. This includes a power surge, physical damage, and manufacturing defects. You need to know how you can diagnose a refrigerator relay for stability. You can do a short test yourself at home. Electrical measuring instruments must be available.
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First you need to find out whether the spare part is located correctly. The norm is strictly vertical. Then you need to remove the part, check its integrity and contacts. They may become acidic or dirty, then they should be carefully treated with fine sandpaper. Contact between terminals can be checked using a tester. It is better to remove noticed rust with a special solution. The presence of traces of burning means only one option - the part is faulty and must be replaced.
Using the “diagnosis” procedure, it is worth testing whether the voltage is correct for the compressor (you should use an ohmmeter or multimeter).
The parameters obtained as a result of the measurement are compared with those declared for this refrigerator model. If the actions do not lead to a positive result, you can call a specialist to your home. On site, a specialist with special knowledge and skills will be able to determine how much repairs cost, how to check the refrigerator start relay for functionality most effectively, and where else the breakdown may be located.
Where is the relay located
The initial installation location is determined by the manufacturer based on their size, type and model. You can see where it is and check the relay by removing the back panel of the refrigerator. In this case, be sure to follow electrical safety precautions.
Thermal relay circuit
The thermostat in a refrigeration unit plays the role of a device that maintains operation at a given temperature by periodically turning the compressor on and off. At the present stage, 2 types of thermal relays are used:
- Mechanical devices are used in old refrigerators, as well as in such modern manufacturers as Indesit, Stinol, Atlant.
Mechanical thermostat diagram
This device is of a manometric type. The bellows and its tube (sealed corrugated metal container) are filled with freon or chlormethyl, which is in the form of steam. The pressure of the working medium changes directly proportionally with temperature changes. At the end of the tube, freon is in a liquid state and is pressed against the evaporator.
As the temperature increases, the pressure of the bellows on the spring increases, the lever is activated, and the contact closes. When the temperature decreases, the opposite happens. The contact opening mode depends on the spring force, which is adjusted by the control knob.
- Electronic thermostats are used in refrigerators from manufacturers such as Samsung, Beko, LG.
Mechanical thermostats rely on the temperature in the evaporator in their operation, while electronic thermostats rely on the air temperature in the chamber. The positive aspect of electronic models is the ability to display temperature (that is, a person can visually assess the operation of the thermostat) and less error.
Electronic thermostat circuit
The temperature controller in this circuit is the LM335 temperature sensor. The device is a zener diode, sensitive to temperature changes. The climate in the refrigerator chamber is regulated by variable resistance R4. When the air temperature rises, a signal appears at the output of the TLC271 comparator, opening the KT3102 transistor, which starts the refrigerator. Accordingly, when the temperature drops, zero appears at the output of the comparator and the compressor turns off.
Checking the refrigerator relay for functionality
If the refrigeration unit does not turn on or does not turn on regularly, then most likely the problem is with the start relay. The reason for its malfunction may be:
- Oxidation or burnt contacts.
- Mechanical damage.
- Overheating of the posistor element.
- Failure to secure the relay, leading to its incorrect positioning.
- Spiral burnout.
- Core jamming.
There is no need to rush to buy a new refrigerator relay, it is better to find out how to test it and try to do it.
In the induction mechanism, the solenoid is pulled out, the contacts are checked, and if oxidized, they are cleaned with sandpaper. The core may be broken, then it needs to be replaced. Wipe contacting surfaces with alcohol. Check the integrity of all elements. It must be remembered that relays of this type are installed strictly in a certain direction, indicated by the arrow. After the above steps, connect the relay to the compressor and turn on the refrigerator. If the engine does not start, then most likely the compressor is broken.
Checking RTP-1 and RTK-X devices
To check, place the relay in the correct position (arrow up) and ring contacts 1 and 3 with a multimeter.
RTK-X device diagram
If the contacts ring, then the relay is working properly. In these models, a visual inspection is advisable, since a short circuit can occur through the contact holder plate.
Checking DXR and LS-08B devices
The DHR needs to be placed with the terminal strip facing up and checked with a multimeter for continuity between 1 and 3 or 1 and 4.
Place LS-08B with the inside facing up, ring between 2 and all terminals or between 3 and all terminals. Where the contacts do not ring through, look for the fault there.
Sequence of checking the functionality of the refrigerator start-up relay
Often, the start-up protection relay of a refrigerator is beyond repair, so repairing a refrigerator comes down to purchasing and completely replacing the relay. But first, you should make sure that the cause of the malfunction is really in it. So how can you check if it works?
Step #1: Inspect the Contacts
The start relay is located in the back of the refrigerator near the compressor, so there shouldn't be any problems finding it. In different models of refrigeration devices, it is either rigidly fixed to the terminals of the compressor motor, or connected to the compressor with flexible wires. In any case, first remove the cap from the start-up coil and inspect both contact groups - upper and lower.
If the contacts are dirty or oxidized, they should be cleaned with fine sandpaper. It may be necessary to slightly bend the bar of the lower contact pair to make the contact tighter.
Step #2: Inspect the Stem
When electric current is applied, the top plate of the starting relay rises, and to prevent the plate from flying off, a guide rod is provided.
Over time, it can become rusty or dirty, preventing the record from playing smoothly. Then the relay stops working properly. The stem should be cleaned with any anti-rust solution. If it can no longer be cleaned and the contact strip cannot move freely, you will need to install a new refrigerator start relay.
Smooth running of the contact group is a necessary condition for normal operation, since the entire procedure for starting the motor should take 2-3 seconds. And if during these seconds the bar simply physically cannot rise and close the contacts, then the launch does not occur or occurs intermittently.
Step #3: Ring the refrigerator start relay
If external inspection and cleaning do not produce results, you should ring the part and look for an open circuit. You should ring with a tester in resistance measurement mode. Take a photo of the connection diagram (just in case it turns out that there is no protection against incorrect connection), remove it from the refrigerator and test the contacts.
If the tester indicates the integrity of the electrical circuit, then the relay is working properly. If not, an urgent replacement of the part is needed.
Checking the thermostat
If your refrigerator does not turn off for a long time, constantly works or does not turn on at all, then the thermostat may be to blame. The culprit must be dismantled, and a jumper must be placed on the remaining contacts. If the refrigerator turns on, check the thermostat itself. It is placed in a container with cold water, and the outputs are tested with a tester or the resistance at the output is measured.
Dialing contacts with a tester
If there is no sound signal or if resistance is present, the thermal relay is faulty and must be replaced.
How to check and repair
There are several ways to check the thermostat of Indesit or any other refrigerator at home. The main ones:
- Checking the bellows. This way you can evaluate the serviceability of the element without removing or disassembling it. However, some skills are required to carry out the work. If a person understands the thermal relay device, he will quickly find a plate located near the small axis to which the regulator is connected. They try to move the bar by turning the handle. If the plate is firmly attached, it does not move and does not make clicks, the relay needs to be replaced.
- Tester check. When repairing household appliances, it is recommended to use a multimeter. To check, the thermostat is removed. If replacement is necessary, it will still have to be removed. The multimeter is switched to ohmmeter mode. Contact resistance should be minimal.
- Check with cold water. It happens that the temperature sensor works normally after removal, but after installation in the refrigerator the part begins to function incorrectly. This is explained by a rare breakdown in which the regulator cannot open and close contacts. At high temperatures the element works normally. To check, place the part in a glass of cold water. After a few minutes, the relay needs to be ringed with a multimeter switched to circuit test mode. The appearance of the number 1 on the tester screen indicates a breakdown.
The procedure for repairing a thermostat includes the following steps:
- search for details;
- disconnecting the capillary tube from the evaporator or removing it from the housing;
- disconnecting the temperature controller;
- replacing the bellows tube with a corresponding new part;
- securing the plate to the evaporator;
- connecting all the necessary wires and returning the relay to its previous position.
