Sudden stoppage of operation refrigerator often takes you by surprise, causing panic due to the risk of food spoilage. However, the cause of a breakdown is not always the failure of an expensive compressor or a refrigerant leak. In most cases, the problem lies in a small but critical element - start-protective relay. It is this component that is responsible for starting the engine and protecting it from overloads.
Understanding how to check a refrigerator relay can save you a significant amount of money on calling a technician and buying a new part. Diagnostics of this unit is accessible even to a person without deep knowledge in electrical engineering, if he acts carefully and follows safety precautions. In this article, we will analyze the structure of the mechanism, the symptoms of its malfunction and the testing algorithm using a multimeter.
Before starting disassembly, you need to make sure that the refrigerator is disconnected from the power supply. Any manipulation of live electrical components is strictly prohibited and dangerous to life. Next, you should determine the location of the relay, which is usually located in the lower part of the unit, in close proximity to the motor-compressor.
Design and principle of operation of the start-up relay
The start-up relay is an electromechanical switch that controls the supply of voltage to the compressor windings. When the refrigerator is turned on, the starting winding requires a high current to create a starting magnetic field. As soon as the motor rotor begins to rotate, the current drops and the relay opens the starting winding circuit, leaving only the working winding active.
The second important function of the device is thermal protection. Inside the case there is a bimetallic plate that bends when heated. If the compressor operates in emergency mode or the current exceeds the norm, the plate opens the contacts, de-energizing the engine and preventing its combustion. Modern models often use PTC relays (posistors), the operation of which is based on a change in the resistance of the semiconductor element when heated.
- 🔌 Contacts: provide a connection between the power circuit and the motor windings.
- 🔥 Bimetal plate: reacts to overheating and current, breaking the circuit.
- ⚙️ Core and coil: create the necessary magnetic field for switching (in electromagnetic models).
Design may vary depending on the manufacturer of the refrigerator, be it Indesit, Atlant or Bosch. However, the basic principle remains unchanged: give a start impulse and turn it off when operating speed is reached. Understanding this logic helps to quickly diagnose why the engine hums but does not start, or is completely silent.
Main signs of a relay malfunction
You can determine that the problem lies in the starting mechanism by characteristic external signs. Often the refrigerator behaves unnaturally, making sounds that were not previously characteristic of it. Ignoring these signals can lead to more serious damage, including compressor wedge.
⚠️ Warning: If you hear a loud click, followed by a motor hum, and then another click and silence, this is a classic symptom of a “false start.” The engine tries to start, but the relay does not open the starting winding or transmit voltage to it.
Among the most common symptoms are also the absence of cold when the fan is running (in No Frost systems) and strong heating of the compressor housing. Sometimes the relay may simply not click when the refrigerator is turned on, indicating a lack of response to the supply of voltage. In such cases, a visual inspection may reveal melting of the plastic or the appearance of burning.
It is important to distinguish a relay malfunction from problems with the compressor itself. If the engine hums but does not start, and the relay is working properly, the piston group may be jammed. However, statistics show that replacing the relay solves the problem in 70% of cases of such symptoms. Diagnostics begins with dismantling the part.
Removing the relay: step-by-step instructions
To carry out high-quality diagnostics, it is necessary to remove the relay from the housing. This process requires a minimal set of tools, usually a flathead screwdriver and pliers are sufficient. Before starting work, make sure that the power cord is unplugged from the outlet and that access to the bottom of the refrigerator is clear.
First remove the rear protective panel if it blocks access to the compressor. Look for a black cylindrical or box-shaped piece attached to the side or top of the motor. Disconnect the wires that go to the relay, having first noted or photographed their location. Then carefully remove the part itself from the compressor contacts.
☑️ Checklist before dismantling
When removing a part, be careful not to use excessive force so as not to damage the fragile plastic clips. If the relay is stuck or very dirty, it can be carefully cleaned with a dry cloth before inspection. Some models are fixed with a metal bracket that needs to be bent.
After removal, carefully inspect the case for cracks, signs of burning or melting. The presence of a burning smell inside the relay housing is almost guaranteed to indicate its malfunction. However, the appearance does not always reflect the internal state of the contacts, so an instrumental test is necessary.
Diagnostics with a multimeter: contact continuity
The most accurate way to check is to use a multimeter in resistance measurement mode (Ohm). This device allows you to assess the integrity of the electrical circuit and the condition of internal contacts. If you don’t have a multimeter, you can purchase one at any electrical goods store, as this is a basic tool for a home craftsman.
First, put the device in the dialing or resistance measurement mode. Touch the probes to the input and output contacts of the relay. In normal condition, the resistance should be close to zero or several ohms, which indicates the integrity of the circuit. If the device shows one or infinity, then the circuit is broken.
| Test type | Normal reading | Failure sign | Action |
|---|---|---|---|
| Coil resistance | Several Ohms (up to 30 Ohms) | Infinity (break) | Relay relay |
| Contacts (closed) | 0 Ohm (beeps) | High resistance | Cleaning or replacement |
| Thermal protection | 0 Ohm (cold) | Infinity | Replacement relay |
| Posistor (PTC) | Low (cold) / High (hot) | Does not change resistance | Replacing relay |
Special attention should be paid to thermal protection. When cold, it should ring briefly. If the multimeter shows a break even at room temperature, it means that the bimetallic strip is deformed or the contacts are oxidized. It is almost impossible to restore such a part; installation of a new component is required.
Nuances of checking posistors
In a PTC relay, the resistance depends on temperature. When cold it should be low (3-50 ohms). If you heat the element with a hairdryer, the resistance should increase sharply to thousands of ohms. If there are no changes, the posistor is faulty.
Visual inspection and mechanical check
Even if the electrical parameters are normal, mechanical defects can interfere with normal operation. Inside the relay housing there is a movable core or rod that must move freely. Contamination or corrosion can block this mechanism, preventing the contacts from closing or opening in a timely manner.
Carefully open the relay housing if its design allows this to be done without destruction. Pay attention to the condition of the contacts: they must be clean, free of carbon deposits and shells. Blackened contacts can be carefully cleaned with fine sandpaper or a file, but this is a temporary measure.
⚠️ Attention: Be careful when disassembling the relay. Springs and small parts may fly apart. If you are not confident in your abilities during assembly, it is better not to disassemble the device completely, but limit yourself to external diagnostics.
Also check the mobility of the rod. It should not stick or be difficult to move. In electromagnetic relays, the core must retract when voltage is applied. For such a test, you will need to apply current from a safe source, which is risky to do at home without the appropriate skills.
Replacing the relay and testing the system
If the diagnostics reveal a malfunction, the only correct solution will be to replace the part. The selection of a new relay is carried out according to the markings indicated on the body of the old element. It is important to take into account the power of the compressor and the type of refrigerant, since the protection response parameters depend on this.
Install the new relay in place, connect the wires according to the previously made diagram or photograph. Make sure all connections are tight and secure. After assembly, do not rush to load food into the refrigerator. First, carry out a test run.
Plug in the refrigerator and listen. The launch should be confident, without prolonged buzzing and repeated clicks. The compressor should operate evenly. If within 15-20 minutes the motor does not turn off and begins to gain temperature in the chamber, then the repair was successful.
In some cases, even after replacing the relay, the problem may persist. This indicates that the compressor itself is faulty or there are problems with the wiring. However, such situations are less common. Most often, replacing the starting device completely brings the equipment back to life.
Frequent questions and answers (FAQ)
Is it possible to repair a refrigerator relay yourself?
In most cases, repair is impossible, since the relay body is sealed, and the internal components (posistor, bimetallic plate) cannot be restored. It’s easier and safer to buy a new part, which is inexpensive.
Why does a new relay burn out quickly?
This may happen due to a selected part with unsuitable current or power parameters. The cause may also be a malfunction of the compressor itself, which consumes too much current when starting.
Where can I find the relay markings?
The marking is usually applied to the side or top of the relay housing. Look for designations like RAT, RT, P and digital codes indicating compatibility with compressors of a certain power.
Is it dangerous to operate a refrigerator with a faulty relay?
Yes, it is dangerous. The compressor may not start, overheat or operate in emergency mode, which will lead to its complete failure and possible wiring fire.