A sudden stop of the refrigerator often causes panic, but in most cases the reason lies in a small, inexpensive part - the start relay. It is this component that is responsible for starting the compressor motor, and if it fails, the unit stops freezing, although the motor itself may be fully operational. Diagnostics of this part does not require deep engineering knowledge, but requires attentiveness and a basic tool such as a multimeter.
Before calling a technician or going to the store for a new spare part, it is worth conducting an initial check, which will help to accurately determine the nature of the breakdown. In this article, we will examine in detail how to visually and technically assess the condition of the relay, which indicators of the device are considered normal, and which indicate a malfunction. You will learn how to safely remove the part and take measurements to make the right repair decision.
Signs of a faulty start relay
Understanding the symptoms is the first step to successful repair. Start relay in the refrigerator it works like a switch that supplies current to the motor windings. When a part burns out or the contacts stick, the compressor's power circuit is disrupted. Most often, you can hear a characteristic click, followed by silence or a hum that lasts several seconds, after which the refrigerator becomes silent again.
The second obvious sign is overheating of the rear wall in the area of the motor. If you touch the compressor, it may be hot even though the unit itself has not cooled for several hours. This indicates that the engine is trying to start, but due to a missing phase or high resistance in the relay circuit, it fails. In some cases, the relay may simply not send a signal to start, and the refrigerator will behave as if it were completely disconnected from the network.
⚠️ Attention: If you smell burning plastic or see sparking when you try to start, immediately unplug the refrigerator from the power supply. Continued operation may lead to a fire in the wiring or failure of the compressor itself.
It is also worth paying attention to the cyclical operation. A working refrigerator operates at certain intervals. If it turns on for a couple of seconds and immediately turns off, and then tries to start again a minute later, this is a sure sign that the starting mechanism is blocking the operation of the motor, protecting it from overload. Ignoring these signals can lead to expensive repairs. thermal relay or trigger mechanism block the operation of the motor, protecting it from overload. Ignoring these signals can lead to costly repairs.
Design and types of relays in refrigerators
To properly check the part, you need to understand what exactly you are dealing with. Modern and old refrigerators use two main types of starting devices: induction (electromagnetic) and posistor. Induction relay works based on the magnetic field of a coil, which closes the contacts when starting, and then opens them when the engine picks up speed. Such models often have moving contacts, which can burn out over time.
Posistor relay is a more modern solution that does not have moving parts. Inside it there is a ceramic element (posistor), which, when voltage is applied, heats up and sharply increases its resistance, opening the starting circuit. These devices are considered more reliable, but also fail, often simply cracking due to overheating or losing their properties.
You can visually distinguish them by their appearance and number of contacts. Induction units often appear as cylindrical or rectangular units with a visible coil inside when the cover is removed. PTC posistors are usually made in the form of a compact plastic case. Regardless of the type, the principle of checking with a multimeter remains similar, although there are nuances in the interpretation of resistance readings.
What is the difference between a thermal relay and a starting relay?
A thermal relay (thermal relay) serves to protect the engine from overheating and opens the circuit at critical temperatures. The starting relay is responsible only for the moment the engine starts. They are often combined into one housing, but technically perform different functions.
Removing the relay: step-by-step instructions
Before starting any work, you must completely turn off the power to the refrigerator. Unplug the cord from the outlet and move the unit away from the wall to provide access to the rear panel. Compressor usually located at the bottom of the rear wall and covered with a metal or plastic casing, which must be removed by unscrewing the mounting bolts or removing the latches.
On the compressor you will see a box containing which the electrical cable fits. This is the relay housing. Carefully remove it, having previously photographed the wiring diagram so as not to mix up the contacts during assembly. In some models, the relay is simply put on three pins of the compressor, in others it is fixed with a metal bracket or plastic clips.
☑️ Safe dismantling of the relay
After removing it from the housing, inspect the part for external damage. If you see cracks, melted plastic, blackened contacts, or smell a burning smell, further inspection may be formal - the part requires replacement. However, to be completely sure, it is better to ring the circuit with a device, since internal defects are not always visible to the eye.
Checking the relay with a multimeter
For diagnostics, you will need a multimeter switched to resistance measurement mode (Ohms). If you have an induction relay, you need to check the coil resistance. Normal readings range from 30 to 60 ohms, although the exact readings vary by model. If the device shows infinity (open circuit) or zero (short circuit), the coil is faulty.
Checking the contacts is carried out as follows: one probe is placed on the input contact, the other on the output contact. In the initial position (the relay is inverted, as on a compressor), the contacts should be open, and the device should show infinity. If you turn the relay to the operating position (imitation of operation), the contacts should close and the resistance should drop to zero. For posistor relays, it is important to check the resistance of the posistor itself: when cold, it should be low (20-60 Ohms).
Pay special attention thermal relayif it is placed in a separate block or is part of the structure. Its contacts should ring when cold (show zero). If the circuit does not ring, it means that the bimetallic plate has already opened and does not return to its original position, or the contacts are burnt and do not conduct current.
| Check Type | Normal readings | Symptom of malfunction |
| :--- | :--- | :--- |
| Coil Resistance | 30-60 ohms | Infinity or 0 Ohm |
| Contacts (closed) | 0 Ohm | Is there resistance or infinity |
| PTC resistor (cold) | 20-60 ohms | Significant deviation from the norm |
| Thermal protection | 0 Ohm (closed) | Infinity (open circuit) |
Table of typical faults and solutions
Analysis of the test results allows you to get a clear picture of the condition of the unit. Below is a table that will help you systematize the data received and choose an action strategy. You should not ignore even the slightest deviations, since operating the engine in abnormal mode reduces its life.
If you find that the contacts are burnt, but the relay is mechanically intact, some craftsmen try to clean them with a needle file. However restored relay rarely works for a long time, since the metal structure is damaged by sparking. In the case of posistors, repair is impossible in principle - ceramics cannot be restored.
⚠️ Attention: The technical characteristics of the relay may vary depending on the compressor manufacturer (Danfoss, LG, Samsung, Atlant). Always check the markings on the part body with the catalog data before purchasing a replacement.
It is also important to consider that relay failure is often a consequence of other problems. For example, if there is little freon in the system or the capillary is clogged, the compressor operates with overload, which leads to overheating and burnout of the starting winding or relay. Therefore, after replacing a part, it is advisable to check the pressure in the system or the temperature of the condenser.
Replacing the relay and first start
The process of installing a new part is the reverse of the dismantling process. Make sure that you purchase a relay with identical markings or a complete analogue suitable for your compressor model. Installing the relay must be carried out strictly in a certain position, indicated by the "UP" or "TOP" arrow on the housing. If you mix up the top and bottom, the mechanism will not work.
Push the relay onto the compressor pins until it stops, making sure that the contacts fit tightly. Connect the wires according to the photo you took earlier. Secure the housing and install the compressor protective cover in place. Only after all elements have been completely assembled can you turn on the refrigerator.
After turning on, listen to the operation of the unit. Startup should be smooth, without buzzing or clicking. The compressor should pick up speed and run smoothly. During the first hours of operation, monitor the temperature in the chambers and the heating of the motor. If all parameters are normal, the repair can be considered successful.
Frequently asked questions during diagnostics
Is it possible to start a refrigerator without a relay?
Technically, you can start the engine by applying voltage directly to the starting winding, but doing this is strictly not recommended without special skills and equipment. This is dangerous and can permanently kill the compressor. The relay is necessary for correct phasing and protection of the motor.
Why does a new relay burn out after a short time?
Most often, the reason lies in a malfunction of the compressor itself (interturn short circuit, jamming) or problems in the electrical network (voltage surges). Also, the cause may be a freon leak, which causes the motor to overheat.
Where can I find the markings for selecting an analogue?
The markings are usually applied to the side or top edge of the relay housing. Look for codes like PTM, R600, 117H, etc. If the inscription is erased, look for the compressor model (on the sticker next to it) and select a relay from compatibility catalogs.
How much does it cost to replace a relay in the service?
The cost consists of the price of the part itself (usually inexpensive) and the work of the technician. Self-replacement saves up to 70% of the amount that would have to be paid at a service center, since the main expense is a visit and diagnostics.