Sudden silence of the refrigerator or, on the contrary, its constant attempts to start and instant shutdowns are a sure sign of a malfunction in the engine starting system. Most often, owners of household appliances are faced with a situation where thermal relay opens the circuit, protecting the motor from destruction. This is a protective mechanism that responds to a critical increase in temperature or current.
If your unit has stopped freezing and the compressor is hot to the touch, you cannot ignore the problem. Long-term operation in this mode or constant on-off cycles can lead to failure of the most expensive component - the compressor. In this article, we will analyze in detail the physics of the process, the causes of overheating and methods of self-diagnosis.
Understanding the operating principle of the starter protection device will help you avoid unnecessary expenses on calling a technician to simply replace a part or, conversely, notice a serious breakdown in time. Modern refrigerators equipped with complex electronics, but basic motor protection often remains electromechanical.
The operating principle of the start-up protection relay
To understand why the protection is triggered, you need to understand the design of the unit. The start-up protection relay is a compact unit installed directly on the contact group of the compressor. Inside it there are two independent systems: starting and protective. The starting one is responsible for short-term voltage supply to the starting winding, and the protective one monitors the current and temperature.
The main element of protection is the bimetallic plate. It is made of two metals with different coefficients of thermal expansion. When an electric current passes, the plate heats up. If the current exceeds the rated current or the motor housing overheats, the plate bends and mechanically opens the contacts, de-energizing the motor.
After cooling, the plate returns to its original position and the circuit is closed again. This cycle can be repeated many times until the cause of the overload is eliminated. It is this click of a cooling or heating relay that you can hear if you come close to a working (or trying to work) refrigerator.
Is it possible to temporarily remove the relay?
Theoretically, you can start the motor without a relay by closing the contacts directly, but this is extremely dangerous. The compressor will burn out in a few seconds or minutes, as it will be left without protection against overheating and short circuit of the windings.
Main causes of compressor overheating
The operation of a thermal relay is always a consequence, not a cause. The root of the problem lies in conditions that lead to excessive heat generation in the motor windings or mechanical jamming. The first and most common reason is a violation of heat exchange.
If the condenser (the grill at the back of the refrigerator) is covered with a thick layer of dust, animal hair or fat, heat is not released into the atmosphere. The pressure in the system increases, the motor operates with increased load, the current increases, and the bimetallic plate of the relay opens the circuit. Regular cleaning of the back wall is a mandatory preventative procedure.
The second reason lies inside the refrigeration circuit itself. A clogged capillary tube or a malfunction of the thermostat results in the compressor running non-stop. In normal mode, the engine should rest. Constant operation leads to the accumulation of heat, which the protection relay does not have time to remove, and an emergency shutdown occurs.
- 🌡️ Circulation disturbance: insufficient clearance between the back wall of the refrigerator and the furniture or wall prevents natural air convection.
- 🧊 Problems with refrigerant: leakage of freon or, conversely, its excess refilling changes the pressure in the system, causing the engine to operate in abnormal mode.
- 🔌 Voltage surges: An unstable power supply can cause short-term current surges, which are perceived by the relay as an emergency.
Malfunctions of the relay itself and the electrical circuit
Sometimes the problem lies not in the motor, but in the protective device itself. Over time, the contacts inside the relay can burn, oxidize, or stick. If the contact is poor, increased resistance occurs at the connection point, which leads to local overheating and false operation of the protection.
It is also worth considering the natural wear of the bimetallic strip. After thousands of heating and cooling cycles, the metal “gets tired” and can change its properties, starting to operate at lower currents than those provided by the manufacturer. In such cases, the relay requires replacement.
It is important to check the integrity of the windings of the motor itself. If an interturn short circuit occurs, the winding resistance drops and the current increases sharply. In this case, the thermal relay is triggered instantly, protecting the apartment's wiring from fire, but signaling that the compressor is faulty. Diagnostics begins with a visual inspection. Remove the back cover and locate the black cylindrical or box-shaped element on the compressor. If traces of melting, soot, or a burning smell are visible on the plastic, the part definitely requires replacement. compressor faulty
Diagnosis begins with a visual examination. Remove the back cover and locate the black cylindrical or box-shaped element on the compressor. If traces of melting, soot, or a burning smell are visible on the plastic, the part definitely requires replacement.
Mechanical reasons and motor jamming
The most unpleasant scenario is mechanical jamming of the compressor piston group. This can happen due to exhaustion, moisture entering the system, or destruction of internal parts. When attempting to start, the motor creates maximum torque, but since the shaft cannot turn, the current in the windings reaches peak values.
The thermal relay detects this jump and breaks the circuit. A characteristic sign of such a breakdown is sound: you hear the hum of the motor, the click of the relay, then silence, and after a while the cycle repeats. This is the so-called “humming” - the sound of the engine operating under load without rotation.
Attempts to “unwedge” the compressor by applying increased voltage or mechanical impact at home rarely give long-term results. Most often, such a unit only needs to be replaced.
Diagnostics and testing with a multimeter
To accurately determine the malfunction, you will need multimeter Before starting any work, be sure to disconnect the refrigerator from the power supply! Remove the housing from the compressor and carefully disconnect the relay. It is usually simply removed from the pins or fixed with a bracket.
The test begins with testing the contacts. Switch the multimeter to resistance (ohms) measurement mode. Check the integrity of the bimetallic strip: the resistance should be close to zero (short circuit). If the device shows infinity (one in the most significant digit), it means that the circuit is broken and the relay is faulty.
Next, we check the trigger mechanism. In some types of relays (posistor) the resistance should be in the range of tens or hundreds of ohms. If the posistor is broken or has infinite resistance, starting the engine is impossible. Also inspect the internal cavity of the relay for dirt and oxides.
☑️ Algorithm for checking the relay
If there are no visual defects, and the tester shows normal, perhaps the problem lies in the compressor itself or the cooling system. However, if the relay “cracks” during operation or has play in moving parts, it is better to replace it, since it is a consumable item.
Table: Comparison of symptoms and probable causes
For ease of diagnosis, let’s summarize the main symptoms in a table. This will help you quickly navigate the nature of the malfunction.
| Symptom | Probable cause | Action |
|---|---|---|
| The refrigerator hums, clicks and does not start | Stuck compressor or winding break | Checking the windings, replacing the compressor |
| The motor runs for 1-2 minutes, then clicks and stops | Thermal relay is activated (overheating) | Cleaning the condenser, checking freon |
| The relay emits a burning smell, melting is visible | Failure of the relay itself | Replacing the starter protection device |
| The compressor is cold, but does not turn on | Malfunction of the thermostat or electronics | Diagnostics of the control circuit |
Procedure for replacing a thermal relay
If diagnostics showed that the relay is faulty, replacing it does not require special skills, but requires care. The main rule: buy a relay with exactly the same markings as the old one. There are no universal solutions here, since the current characteristics and mounting geometry differ for different compressor models.
Remove the old relay, remembering or photographing the position of the wires. Usually there are only two or three contacts. Install the new part, pushing it tightly onto the contact group of the compressor until it clicks or stops. Make sure that the relay sits level and does not wobble.
After installation, turn on the refrigerator. The norm is to start the compressor within the first 5-10 seconds. If the motor runs smoothly, without buzzing or repeated clicks, the repair can be considered successful. Let the unit run for 30-40 minutes and check whether the new unit is overheating.
⚠️ Attention: When replacing the relay, make sure that the pins on the compressor are not oxidized. If they have a green or black coating, carefully sand them with fine sandpaper before installing a new part to ensure reliable contact.
Prevention and expert recommendations
To avoid a recurrence of the situation, it is important to follow the operating rules. Do not install the refrigerator close to the wall, leave a gap of at least 10 cm for air circulation. Regularly check the tightness of the door and the condition of the seal - if warm air enters the chamber, the compressor will work with overload.
Also monitor the room temperature. If the refrigerator is located in the kitchen, where the temperature rises above +30°C in summer, its efficiency decreases and the load on the motor increases. Under these conditions, more frequent maintenance may be required.
Do not load the storage compartment with too much warm food. A sharp jump in temperature inside forces the cooling system to work at its limit, which triggers the protection.
Is it possible to use a relay from another brand?
The use of analogues is possible if the current characteristics (indicated on the case, for example, 1/4 HP or specific Amps) and mounting dimensions match. However, original parts are always preferable.
⚠️ Attention: If after replacing the relay and cleaning the system the situation repeats after a short time, do not continue attempting to start. This is a sign of a deep malfunction of the compressor or refrigerant circulation system, requiring professional intervention.
Frequently asked questions (FAQ)
Is it possible to repair a thermal relay yourself by cleaning the contacts?
Theoretically, you can disassemble the case and clean the contacts, but this is a temporary measure. The bimetallic strip is a precision element and any tampering may disrupt the calibration. The cost of a new relay is low, so it is more reliable and safer to make a complete replacement.
Why does the relay click, but the compressor does not even hum?
This may indicate that the voltage reaches the relay, it operates, but does not transmit current further due to a break inside, or the problem is in the compressor itself (winding break). It is also worth checking the starting capacitor, if it is in the circuit.
How often should the thermal relay be changed?
This element does not have a strict expiration date. It changes only in the event of a malfunction. With normal operation and the absence of voltage surges, the relay can last as long as the compressor itself (10-15 years).
Is it dangerous to operate a refrigerator with a frequently triggered relay?
Yes, it is dangerous. Constant starting currents and overheating can lead to a wiring fire or final failure of the compressor, the replacement of which is often not economically feasible.