A sudden stop of the refrigerator or a characteristic click followed by silence often indicates problems in the motor electrical circuit. Start protection relay is one of the key elements that ensures the start and safe operation of the compressor. It is this small component that is responsible for supplying voltage to the starting winding at the time of start and turns it off when the motor picks up the required speed.
If you are faced with a situation where the motor hums but does not start, or turns on for just a few seconds and immediately stalls, most likely you need to check this devices. Relay subject to natural wear, current overloads and mechanical damage, especially in older models of equipment. Understanding the principle of its operation will help you quickly diagnose a breakdown without calling a technician.
In this article we will analyze in detail the structure of the mechanism, the symptoms of its failure and provide step-by-step instructions for checking using a multimeter. Diagnostics takes a little time, but allows you to save significant money on repairs if the problem lies precisely in this inexpensive part. The main thing is to follow safety precautions and do everything consistently.
Design and principle of operation of the trigger mechanism
To effectively check a part, you need to understand how it works. Most household refrigerators use electromagnetic or posistor relays. Electromagnetic the device operates on the principle of core retraction: when current is applied, the coil creates a magnetic field, closing the contacts of the starting winding. As soon as the motor rotor begins to rotate, the current drops and the spring opens the circuit.
Posistor Models that are more often found in modern technology use a thermocouple. When current passes, the posistor heats up and sharply increases its resistance, actually breaking the starting winding circuit. After cooling (which takes several minutes), it conducts current again, allowing you to try to start again. Design may differ, but the function remains the same - to ensure the start of the motor and protect it from overheating.
There is also a thermal heater inside the case release - a bimetallic plate that opens the circuit when the current increases critically. This is protection against burning of the motor windings. If the relay is “stuck” in the closed state, the compressor may burn out, so the serviceability of this unit is critical for the longevity of the entire cooling system.
⚠️ Attention: There may be mercury vapor (in very old models) or toxic combustion products of plastic inside the relay. Do not forcefully open the sealed case or heat it with open flame. If there are cracks or melting, the part must only be completely replaced.
What is the difference between relays from different manufacturers?
Electromagnetic relays (often labeled as RTP, RTK) are typical for Soviet-made refrigerators and early Atlant models. They have a movable core and coil. PTC (marking often contains the letters PTC) are used in Indesit, LG, Samsung. They do not have moving mechanical parts, except for a thermal release, and are considered more reliable, but are sensitive to voltage surges.
Main signs of a relay malfunction
You can determine that the problem lies in the starting device by the characteristic symptoms. The most obvious sign is when the compressor tries to start, there is a loud click, the motor hums for a few seconds, and then there is another click and silence. This cycle can be repeated endlessly until you unplug the device. This indicates that starting winding does not receive a pulse or does not turn off in time.
Another symptom is the complete failure of the refrigerator when the lighting inside the chamber is on. If the light is on, it means that voltage is supplied to the network, but the engine is silent. In this case, the compressor itself may be hot to the touch, which indicates attempts to start or overheating due to jammed contacts. Thermal protection in this case, it works correctly, preventing a fire, but cold does not appear in the chambers.
It is also worth paying attention to the appearance of the part. If during a visual inspection you notice blackened contacts, melted plastic, or smell a burning smell, there can be no doubt. Mechanical damage to the housing or the presence of oxides on the terminals is also a direct indication of the need for replacement. Visual inspection Often provides more information than complex measurements.
Preparation for diagnostics and safety precautions
Before proceeding with removing and checking elements, It is necessary to completely turn off the power to the refrigerator. Unplug the power cord and make sure the back wall is clear. You will need a minimum set of tools: flat and Phillips screwdrivers, pliers and, most importantly, multimeter (tester) for checking the continuity of the chain. Without a device, accurate diagnosis is almost impossible.
Remove the back cover at the bottom of the unit where the compressor is located. The relay is usually placed directly on the motor contact rod and secured with a bracket or plastic latches. Carefully disconnect the wires, having previously photographed their location so that during assembly you do not confuse phase and zero. The numbering of the contacts on the diagram printed on the relay body will help you navigate.
Work in a dry room and on a dry floor. Even when the power is turned off, a residual charge may remain in the capacitors, although it is minimal in the refrigerator starting circuit. Avoid touching bare metal parts with your hands during live testing, if such testing will be carried out (although continuity testing is done with the device de-energized). Safety is priority number one.
☑️ Preparing to test the relay
Step-by-step instructions: how to test a relay with a multimeter
The removed device must be cleaned of dust and dirt. Turn it over and inspect the contacts. To check, switch the multimeter to resistance measurement mode (Ohm) or continuity mode. If you have an electromagnetic relay, place it so that the core is in the operating position (usually with the coil facing up). In this position, the contacts of the starting winding should be open.
Attach the tester probes to the corresponding contacts. If the device shows infinity (one on the screen or no sound), then the circuit is open, which is normal for a state of rest. Now flip the relay over (or press the core to simulate starting). The contacts should close, and the multimeter will show zero resistance or close to it. If there is no resistance in any position, the contacts are burnt or the mechanism is jammed.
For posistor models, the procedure is slightly different. They check the resistance of the posistor itself. It should be several tens of ohms (usually from 10 to 50 ohms) at room temperature. If the tester shows an open circuit or, conversely, a short circuit (0 Ohm), the part is faulty. Also be sure to check thermal relay: its contacts in a cold state should ring short (resistance is close to 0).
Below is a table of typical resistance values for serviceable elements:
| Element type | Multimeter mode | Normal reading | Failure sign |
|---|---|---|---|
| Posistor (PTC) | 200 Ohm | 10 – 60 Ohm | Infinity or 0 Ohm |
| Thermal relay (contacts) | Ring | 0 Ohm (beeps) | Resistance or open circuit |
| Electromagnet coil | 2 kOhm | 10 – 100 Ohm | Open circuit |
| Start contacts (closed) | 200 Ohm | < 1 Ohm | High resistance |
Replacement and installation of a new component
If the diagnostics show a malfunction, the only correct solution is replacement. Repair of internal contacts is only possible in a workshop using argon welding and is not practical for household appliances. Buy a similar relay, focusing on the compressor power and the type of refrigerant indicated on the engine nameplate. Compatibility Here plays a key role.
Installation is carried out in the reverse order of removal. Place the new device onto the contact group of the compressor until you hear a characteristic click or stop. It is important to orient the part correctly: on the body there is often an arrow pointing upward or an inscription TOP. Incorrect orientation may result in the thermal release not operating in time, which is dangerous for the motor.
Connect the wires to the terminals according to the photograph or diagram taken earlier. Make sure connections are tight and not oxidized. If the wire terminals are melted, it is better to clean them or replace them. After assembling all the components, you can plug in the refrigerator. The first start may take several minutes, since the posistor needs time to cool down (if it is new) or the system to equalize the pressure.
⚠️ Attention: Do not try to operate the refrigerator with a shorted relay (bypassing the protection). This is a direct path to burning out an expensive compressor. If the new relay clicks, but the motor does not start, the problem may be in the motor itself or an interturn short circuit.
Common mistakes during self-repair
One of the common mistakes is ignoring the cause of the breakdown. If the relay burns out, this is often the result of a power surge or problems with the compressor itself (hard starting). Simply replacing a part without checking the voltage in the network can lead to the new relay burning out in a week. A voltage stabilizer can be a necessary addition to the repair.
Another mistake is incorrect installation of orientation. Many craftsmen forget that thermal protection works based on heat convection or gravity. If you turn the relay upside down, the bimetallic strip may not straighten in time, and the protection will not work if there is an overload. Always look for the position markings on the case.
Also, do not use a relay from another refrigerator model by eye. Even if it physically fits in size, the current characteristics may differ. This will lead either to constant false shutdowns or to operation of the engine in emergency mode. Exact match models are the key to long service.
Prevention and extension of service life
For the start-up relay to serve for a long time, provide the refrigerator with good ventilation conditions. The compressor should not overheat, so the distance from the back wall to the wall should be at least 5-10 cm. Regularly remove dust from the condenser (black grille at the back), as contamination leads to an increase in pressure and current in the system, which increases the load on the starting contacts. Monitor the stability of the electrical network. Frequent power surges destroy not only the electronics, but also the mechanics of the relay. If the lights in your house are “flashing”, think about installing a stabilizer for the entire apartment or at least for the refrigeration group. This will save the resources of the engine and protective fittings. trigger contacts.
Monitor the stability of the electrical network. Frequent power surges destroy not only the electronics, but also the mechanics of the relay. If the lights in your house are “flashing”, think about installing a stabilizer for the entire apartment or at least for the refrigeration group. This will save the resources of the engine and protective fittings.
If the first signs of unstable operation appear (long pauses between starts, unusual sounds), do not delay diagnostics. Timely replacement of a cheap part will save the compressor from major repairs. Prevention always cheaper than restoration after a serious breakdown.
Is it possible to temporarily start a refrigerator without a relay?
Technically, you can start the motor by applying voltage directly to the starting winding, but doing this is strictly prohibited at home. Without thermal protection, the compressor will burn out in a few minutes or a short circuit will occur. This is an emergency measure for diagnostics by technicians, and not a method of operation.
Why does the relay heat up during operation?
Slight heating is acceptable, especially for posistors that operate on heating. However, if the relay body becomes too hot (impossible to hold your hand), this is a sign of poor contact, excessive current, or a faulty compressor. An immediate check is required.
How often should the starting relay be changed?
The service life of the relay is not strictly regulated and depends on operating conditions. On average they last 5-10 years. Replacement is made only in the event of a malfunction. Scheduled replacement is not required if the device is working correctly.
Is a relay from one brand suitable for another?
Yes, if the technical characteristics match: rated current, compressor type (low-speed/high-speed) and mounting method. The brand (Indesit, Samsung, Bosch) is secondary, the parameters indicated on the label are important.