How to ring the refrigerator thermorelay: step-by-step instructions

Sudden stoppage of work refrigeration unit or the absence of a characteristic engine start sound often indicates a malfunction in the electrical control circuit. One of the key elements responsible for starting and operating the compressor is start-up protection relaywhich in everyday life is often called a thermal relay. It is this small component that protects the motor from overheating and provides the necessary starting torque. If the refrigerator hums but does not start, or it turns on for a few seconds and immediately turns off, there is a high probability that this particular unit requires diagnostics.

The verification process does not require deep knowledge in electronics, but requires the presence of basic tools and compliance with safety rules. Before proceeding with disassembly and measurements, you need to make sure that the problem does not lie in the lack of voltage in the network or damage to the power cord. Thermal relay is an electromechanical device that responds to changes in current strength and temperature of the motor windings, opening the circuit at critical values. Understanding the principle of its operation will help you correctly interpret the measurement results and avoid false conclusions about the condition of the compressor.

To carry out high-quality diagnostics, you will need a multimeter (tester), a set of screwdrivers and, possibly, pliers. A voltage of 220 volts is dangerous to life, so do not start checking the contacts while the refrigerator cord is plugged into the outlet. In this article we will analyze in detail the algorithm of actions, symptoms of a malfunction and a method for assessing the condition contacts, which will allow you to make an informed decision about replacing the part or further repairs.

Main signs of a faulty start relay

Before disassembling the back wall refrigerator, it is worth analyzing the behavior of the equipment. The symptoms of a relay failure are often specific and different from problems with a thermostat or a freon leak. If you hear a loud click, followed by a hum from the motor, and then another click and silence, this is a classic sign that the starter winding is not getting impulse or the motor is unable to get up to running. In such situations trigger mechanism it often turns out to be burnt out or stuck.

Sometimes the malfunction manifests itself differently: the compressor works continuously without turning off, while the temperature in the chambers can be either too low or not low enough. This may indicate that the contacts inside the relay have become stuck in the closed state, and the device has ceased to perform its protective function. In this case, the engine wears out, which can ultimately lead to an expensive replacement. It is also worth paying attention to the appearance of the part: the presence of burning, melted plastic or the characteristic smell of burnt insulation immediately after removing the casing indicates the need for urgent replacement.

There are a number of indirect signs that help narrow down the search:

• 🔊 The refrigerator makes repeated clicks every few minutes without starting the motor.
• 🔥 The compressor housing or the relay itself becomes very hot in the lower part of the unit.
• ⚡ When connected to the network, the circuit breakers immediately knock out or the fuse blows.

⚠️ Attention: If after replacing the relay the situation repeats, the problem may lie in the compressor itself (interturn short circuit). Do not install new parts on a faulty engine, this will lead to the burning of the new relay.

Preparation of tools and safety measures

High-quality diagnostics is impossible without the proper tools. The main device for testing is multimeter, which should be able to measure resistance (Ohm) and test the circuit for an open circuit. Make sure that the battery in the device is charged, as if the battery is discharged, the readings may be incorrect. You will also need screwdrivers (Phillips and flathead) to remove the compressor protective casing and fix the terminals.

Before starting work, be sure to disconnect the refrigerator from the power supply. It is not enough to simply turn it off with a button, if there is one, you must remove the plug from the socket. Let the unit sit for 10-15 minutes to allow the capacitors to discharge and the refrigerant to redistribute. Carefully remove the rear protective panel at the bottom of the refrigerator to gain access to the compressor. On the motor nozzle you will see a plastic box - this is the relay you are looking for.

For ease of work, prepare your workplace:

• 🔦 Provide good lighting, since the compressor niche is often dark.
• 🧤 Use dielectric gloves for additional hand protection.
• 📸 Take a photo of connecting the wires before disconnecting them so as not to mix up the contacts during assembly.

Be careful with the copper tubes coming out of the compressor. They are thin-walled and easily damaged if handled carelessly. Do not use excessive force when removing the relay; it may be fixed tightly enough or become stuck over time.

Dismantling and visual inspection of the part

Removing the relay is a process that requires care. Typically, the device is mounted on three terminals of the compressor and is additionally secured with a bracket or plastic clip. You must first remove the retaining clip, if present. Then carefully, rocking from side to side, remove the relay housing from the motor pins. It is important not to damage the insulation of the wires going to the relay.

After removing the device, perform a thorough visual inspection. Shake the relay near your ear: if you hear a ringing or knocking sound inside, this is a sure sign that the insides have crumbled or come off and the part needs to be replaced. Even if the device looks intact on the outside, inspect the contacts for oxidation, carbon deposits, or traces of melting. A RT type starting relay (with a posistor) has a ceramic element inside that should not have cracks.

Disassemble the relay body, if possible (usually it consists of two halves fastened with latches). Inside you will see:

• 🧲 Movable armature with contacts (in electromagnetic relays).
• 🟠 Coated ceramic disk - posistor (in starting relays of modern models).
• 🔌 Contact groups that must close and open.

The presence of a black coating on the contacts indicates a spark jumping and a poor connection. In some cases, the contacts can be cleaned, but for reliable operation of the refrigerator it is better to use a new part. If you see melted plastic inside or smell a burning smell, further checking with a multimeter may no longer be necessary - the device is faulty.

Method of testing with a multimeter (testing)

The most reliable method of diagnosis is checking the electrical resistance using a tester. Switch the multimeter to resistance measurement mode (usually indicated as Ω, limit 200 ohms or 2 kohms). If your device has a beep mode (with a beep), use it to quickly check for an open circuit. First, check the integrity of the probes themselves by connecting them to each other: the device should show zero or make a squeak.

To check a posistor relay (the most common type), you need to find two main contacts. Usually they are located opposite each other. At room temperature, the resistance of a working posistor should be in the range from 3 to 60 Ohms, depending on the model. If the device shows one (infinity), it means that the circuit is in break, and starting the engine is impossible. If it shows zero, it is possible short circuit.

Checking the electromagnetic relay (with a coil) is a little more complicated. Here you need to ring the coil and check the mobility of the contacts. The coil resistance is usually 30-100 ohms. The main thing is to check whether the contacts open in a quiet state and whether they close when pressed forcibly (startup simulation). To do this, carefully press the moving mechanism with a screwdriver (with the power off!) and ring the circuit.

Measurement results can be as follows:

• ✅ Resistance is normal: the relay is working, look for the cause in the compressor or wiring.
• ❌ Infinite resistance: internal break, replacement required.
• ❌ Resistance is close to zero: short circuit, dangerous for the network.

⚠️ Attention: It is better to check the posistor on a cold part. If you just turned off the refrigerator or held the relay in your hands for a long time, its temperature may have risen and the resistance will change, giving a false result. Allow the parts to cool to room temperature.

Table of normal values and decoding

For correct interpretation of the tester readings, it is useful to know Typical values for various relay components. Different manufacturers use different circuits, but the physical principles remain the same. Below is a table that helps determine the condition of the part based on the data obtained.

Please note that the resistance of the thermal relay in a cold state should be close to zero, since it passes current to the motor. Opening occurs only when heated by overload current. If the multimeter shows a break on the thermal relay at room temperature, it means that the protection worked earlier and did not return to its original state, or the element burned out.

Replacement and installation of a new relay

If the diagnostics showed a malfunction, the only correct solution is replacement element. Repairing the internal part of the relay (gluing the posistor, cleaning the contacts) is temporary and does not guarantee safe operation. Buy a new part that strictly matches the markings of the old one. Part numbers are usually stamped on the case or pasted on a label.

Installation is carried out in the reverse order of removal. Insert the relay onto the pins of the compressor, observing the orientation (top/bottom, usually indicated by the UP arrow). Make sure the contacts are pushed in tightly and all the way. Secure the device with a bracket or clamp. Connect the wires according to the photograph or color marking you took earlier. Usually this is not difficult, since the connectors have a unique shape.

After assembly, do not rush to close the back cover. Plug in the refrigerator and listen. There should be a click, followed by the steady hum of the compressor running. If the motor starts and turns off after a while when it reaches temperature, the repair was successful. If the situation repeats (click-hum-click), the problem may be deeper.

⚠️ Attention: Relay specifications may vary depending on the compressor model. Use only original spare parts or high-quality analogues with identical current and voltage parameters. Installing an unsuitable relay can lead to a fire.

Frequently asked questions (FAQ)