The situation when the refrigerator relay gets hot often frightens owners of household appliances, forcing them to assume the worst - a fire or complete failure of the unit. However, in most cases, heating is a natural process of the electromagnetic coil or a sign that the protective mechanism is performing its function. The starting relay is a key component that ensures the start of the compressor engine, and its temperature regime directly depends on the electrical load passing through the contacts and windings.
It is important to understand the difference between warm and hot. If the body of the part is warm to the touch, this may be normal for a running compressor. But if the relay cannot be touched with your hand or a burning smell emanates from it, this is a signal of a critical overload. Thermal relay is specially designed to heat up to a certain temperature at which the bimetallic plate opens the circuit, saving the motor from combustion. Ignoring this symptom can lead to expensive repairs, including replacing the compressor itself.
In this article we will analyze in detail the physical causes of overheating, diagnose malfunctions and determine when you can fix the problem yourself, and when you need to call a technician. You will learn how to distinguish a normal work process from an emergency situation that requires immediate intervention.
⚠️ Attention! Before starting any diagnostic work or replacing the relay, be sure to disconnect the refrigerator from the power supply. Being under 220V voltage is dangerous to life.
The principle of operation of the starting relay and temperature conditions
To understand why the starting relay of the refrigerator gets hot, it is necessary to consider its design. Most modern and older models use electromagnetic devices. When voltage is applied, current passes through the inductor, creating a magnetic field. This field draws in the core, which closes the contacts, supplying power to the compressor starting winding. The passage of current through a conductor is always accompanied by the release of heat according to the Joule-Lenz law.
After the engine picks up speed, the current in the starting winding drops, the magnetic field weakens, and the contacts open under the influence of a spring or gravity. This entire cycle takes a fraction of a second, but at the moment of starting, a current passes through the coil that significantly exceeds the rated operating current of the motor. It is at this moment that the main heating occurs. If the relay remains connected to the network constantly, even when the compressor is stopped, it can noticeably heat up due to residual currents or design features.
There are also solid-state starting relays (posistors)the operating principle of which is radically different. They use a crystal that changes its resistance when heated. When current passes through the posistor, it heats up, its resistance increases sharply, and the current through the starting winding practically stops. For posistors, heating up to 100-130 degrees Celsius is the normal operating mode necessary to perform their function.
- 🔥 Electromagnetic relays heat up due to the resistance of the copper winding of the coil when the starting current passes.
- ⚡ Solid-state relays (posistors) require strong heating to increase resistance and turn off the starting winding.
- 🌡️ The permissible temperature of the housing of a working relay can reach 60-80 degrees, which feels like “hot”, but is not a malfunction.
Thus, moderate heating is a physical inevitability. The only problem is excessive overheating, which indicates an imbalance in the relay-compressor system.
Natural causes of heating: when panic is inappropriate
Many users begin to sound the alarm when they discover that the back wall of the refrigerator and the components located on it are hot. This is often completely normal. During operation, the compressor heats up itself, and the heat is transferred to the parts attached to it. If you touch the relay and it is hot, but the refrigerator freezes properly, the on and off cycles are observed, and there are no extraneous sounds - most likely, the equipment is working normally.
This is especially true for models with inverter compressors or units operating in the hot season. In summer, heat exchange in the condenser is difficult; the compressor is forced to work longer and with greater load in order to maintain the set temperature in the chambers. In such conditions, all elements of the electrical circuit, including the relay, operate at elevated temperatures.
It is also worth considering the location of the refrigerator. If the unit is built into a niche or pushed tightly against the wall, air circulation is impaired. Heat is not removed, creating a “heat bag” effect. In this case, not only the relay heats up, but also the entire motor-compressor. This is easy to check: just move the refrigerator away and let it work with open air access. If the temperature of the nodes has decreased, the reason has been found.
Failure symptoms: how to distinguish normal from breakdown
Despite the permissibility of heating, there are clear signs indicating that the relay has failed or is in a dying state. The first and most obvious symptom is a characteristic odor. If you smell burnt plastic, rubber or scorched wiring coming from the back of the refrigerator, this is a sign of melting insulation or burnt contacts inside the relay.
The second sign is unstable operation of the compressor. The engine may attempt to start, make a loud humming sound, click but not start, and then hear the safety relay disengage. After some time (when the bimetallic plate has cooled), the cycle repeats. This phenomenon is called “cycling” and indicates that the starting relay cannot start the motor, or the compressor is jammed.
The third sign is visual changes. If you remove the casing and inspect the relay, you may notice blackening of the housing, melting of the plastic, or oxidation of the contacts. In some cases, there may be burnt chips inside the case, which is a product of the destruction of the contact group.
| Symptom | Probable cause | Degree of danger |
|---|---|---|
| The relay is warm, the refrigerator is freezing | Normal operating mode | Safe |
| Strong heating, burning smell | Burning of contacts, insulation breakdown | High (risk of fire) |
| Clicks, the motor does not start | Malfunction of the starting mechanism or compressor jam | Critical |
| The compressor hums and turns off | Thermal protection is triggered due to overload | High |
Main causes of overheating and failure
If it is determined that the heating is abnormal, it is necessary to look for the cause. Most often the culprit is the relay itself. Over time, the contacts inside the device burn out and carbon deposits form on them, which increases resistance. The passage of current through an area of high resistance causes local overheating. Eventually, the contacts may “weld” to each other, and the relay will no longer open the circuit, which will lead to constant power supply to the starting winding and rapid combustion of the engine.
Another common reason is a breakdown of the insulation of the relay winding or a short circuit of the coil turns. This often happens in older models where poor-quality insulation was used, or after power surges. In this case, the relay heats up even in standby mode or when the compressor is turned off, if it is not completely disconnected from the network.
However, the relay itself is not always to blame. Overheating is often caused by problems with the compressor. If an interturn short circuit occurs in the motor windings, the current consumption increases sharply. A relay designed for normal currents begins to work in extreme mode, overheating and quickly failing. Replacing the relay in this case will only give a temporary effect - the new one will burn out in a few days or weeks.
The effect of voltage surges on the relay
Sudden changes in voltage in the network can cause short-term but powerful surges of current. This results in microscopic damage to the relay contacts that accumulates over time. As a result, the device loses the ability to normally switch the circuit, sparking and heating begin. Installing a voltage stabilizer can extend the life of not only the relay, but also the entire compressor.
Diagnostics: checking the relay with a multimeter
To accurately determine the malfunction, it is not enough just to touch the part with your hands. You will need a multimeter. First, remove the relay from the compressor. It is usually attached to the side pins of the motor and secured with a metal bracket or plastic latches. Carefully disconnect the wires, having first noted or photographed their location.
Visually inspect the device. Shake it near your ear: if something dangles and rattles inside, it means that the contact group is destroyed or the core has come off. This relay must be replaced immediately. If there are no visual defects, proceed to the “diagnosis”. Switch the multimeter to resistance measurement mode (Ohms).
Check the resistance between the contacts. For an electromagnetic relay, the winding resistance should be several tens of ohms (usually 20-60 ohms). If the device shows zero (short circuit) or infinity (open), the relay is faulty. For posistors, the resistance in the cold state should be low (several Ohms), and when heated, it should go to infinity.
☑️ Algorithm for checking the relay
Replacing the relay: step-by-step instructions
If the diagnostics showed a malfunction, the relay must be replaced. There is no point in repairing this device: the cost of a new part is low, and the reliability of the restored unit will be questionable. It is important to choose an exact copy or a complete analogue. Relays are marked by compressor power and refrigerant type, so old designations (for example, R-3, R-4, RKT) may differ from modern analogues.
The replacement process is simple, but requires care. Remove the old relay by disconnecting the wires. Install the new unit onto the compressor pins, paying attention to the orientation (usually the housing will have a "Top" marking or an "Up" arrow pointing up). Connect the wires to the appropriate terminals. Make sure that the wires do not touch the hot parts of the compressor and are away from moving parts, if any.
After installation, plug in the refrigerator. The compressor should start with a characteristic sound. During the first minutes of operation, carefully monitor the new relay: it should not spark, smoke or heat up excessively. If everything went well, install the protective cover in place.
⚠️ Attention! Never install relays “at random” or universal models without checking the connection diagram. An incorrect connection can lead to instant burnout of the compressor starting winding, the repair of which is not economically feasible.
Frequently asked questions and problems (FAQ)
Is it possible to temporarily short-circuit the relay so that the refrigerator can be completed before the technician arrives?
It is strictly not recommended. Closing the relay prevents the starting winding from being disconnected, which will lead to rapid overheating and combustion of the compressor. You can save on a relay, but you will lose the engine.
Why did the new relay burn out a week after replacement?
Most likely, the reason is not in the relay, but in the compressor itself (interturn short circuit, jamming of the piston group) or problems with the wiring. It is also possible that a relay with unsuitable characteristics was installed.
Does the relay get hot when the refrigerator is turned off?
No, if the refrigerator is unplugged, the relay is cold. If the refrigerator is on, but the compressor is not running (stopping), the relay may be slightly warm, but not hot. Strong heating during idle mode indicates a malfunction.
What is the difference between a starting relay and a protective relay?
Often these are two separate devices, but they can be combined into one housing. The starting one is responsible for supplying current to the starting winding, and the protective (thermal) one opens the circuit in case of overcurrent or temperature. In modern refrigerators, they are often combined in one plastic box.
How long does the starting relay last?
The service life of the relay depends on the number of on-off cycles of the compressor. On average, a high-quality relay lasts 5-10 years. Frequent power surges and overheating of the compressor shorten this period.