How to ring the compressor relay on the refrigerator: diagnostics and repair

If your refrigerator suddenly stops freezing, and the engine runs jerkily or does not start at all, making only a quiet click, most likely the problem lies in the start-protection relay. This small element, often called a “tablet,” is responsible for supplying power to the motor windings and protecting it from overheating. Before calling a technician or buying a new unit, it is worth conducting initial diagnostics, which often allows you to identify a burnt part in a few minutes.

The testing process does not require complex equipment, a basic set of tools and a multimeter are enough. In this article we will analyze the design of various types of relays, consider the algorithm of actions when dialing contacts and identify signs indicating the need for replacement. Understanding how this part works will help you avoid mistakes when repairing household appliances yourself.

Safety is the first thing you need to think about before starting work. Be sure to disconnect the refrigerator from the power supply before touching any internal components. The accumulated electrical charge in capacitors or residual voltage can lead to unpleasant consequences, so do not neglect electrical safety rules even when checking seemingly simple components.

Design and principle of operation of the start-up protection relay

Start-up protection relay is an electromechanical device that controls the connection of the motor starting winding. When the refrigerator is turned on, the current in the circuit increases sharply, and the relay supplies voltage to the starting winding, creating the necessary torque to rotate the rotor. As soon as the engine picks up speed, the current drops, and the mechanism opens the starting winding circuit, leaving only the main winding working.

There are two main types of such devices: induction (electromagnetic) and posistor (thermal). Induction models work due to the movement of the core inside the coil under the influence of a magnetic field. Posistor relays, more modern and common in household appliances, use the property of the semiconductor element to heat up and increase resistance, breaking the circuit when a certain temperature is reached.

In addition to the starting function, many relays combined with thermal protection. Inside the housing there is a bimetallic plate, which bends when the compressor overheats and opens the contacts, preventing combustion of the motor windings. That is why during diagnostics it is important to check not only the start contacts, but also the integrity of the thermal protection.

⚠️ Attention: Inside the relay housing there may be asbestos (in older models) or toxic dust from burnt contacts. Do not open the sealed relay case and do not try to repair it - the part can only be completely replaced.

Necessary tools and preparation for diagnostics

For a quality check, you will need a minimum set of tools that can be found in the arsenal of any home craftsman. The main device will be multimeter (tester), which allows you to measure resistance and check the integrity of the circuit. Make sure that the device is in good working order and its probes do not have insulation damage.

You will also need:

• 🔧 Screwdrivers (Phillips and flat) for removing the back panel and mounting clamps.
• 🔪 Knife or side cutters for neatly cutting wires if the terminals are oxidized.
• 🧤 Dielectric gloves for additional hand protection.
• 📸 Smartphone camera for photographing the connection diagram before disassembling.

Before ringing the compressor relay, you need to gain access to the motor. Remove the back metal cover of the refrigerator by unscrewing the mounting screws. Locate the compressor - usually this is the black “barrel” at the bottom of the unit. A terminal box is suitable for its terminals, in which the desired relay is located.

Carefully remove the plastic casing from the terminal box. It is often secured with a spring clip or screw. Your task is to get to the place where the relay is placed on three contacts of the compressor. Before removing the part, it is strongly recommended to photograph the position of the wires and contacts so as not to mix up the polarity during assembly.

Removing the relay from the compressor

Removing the relay is a procedure that requires care, since plastic elements become fragile over time. First, disconnect the wires going to the relay contacts. In some models they can simply be thrown over the terminals, in others they can be secured with screws. Proceed carefully so as not to damage the insulation of the wires.

The relay itself sits tightly on the three pins of the compressor. To remove it, grab the part by the body and pull it down with a rocking motion from side to side. Do not use excessive force if you feel strong resistance - it is better to slightly pry the housing with a flat-head screwdriver, being careful not to damage the contacts.

After dismantling, carefully inspect the inside of the relay. If you find traces of burning, melted plastic, soot, or smell a strong burning smell, further testing may not be necessary - the part is clearly faulty. However, visual integrity does not guarantee serviceability, so checking with a multimeter is required.

Testing algorithm with a multimeter: step-by-step instructions

The diagnostic process depends on the type of relay you have, but the general principle comes down to measuring the resistance between certain contacts. Switch the multimeter to resistance measurement mode (Ohms), usually the limit is 200 Ohms or 2 kOhms. Connect the tester probes to each other to make sure that the device shows zero.

For posistor relays (the most common option in modern refrigerators Indesit, Atlant, Stinol), the test is as follows:

• 📏 Connect the probes to the contacts responsible for the main winding. The tester should show a resistance in the range of 10–30 ohms.
• 📏 Check the starting winding circuit. The resistance here is usually higher, from 30 to 100 Ohms, depending on the power of the motor.
• 📏 Ring the thermal fuse. In good condition, its resistance should be close to zero (0.1–0.5 Ohm).

If the relay is electromagnetic (often found in older models), a coil and a moving core are visible inside. In this case, the integrity of the coil is checked. The resistance should be small, but not zero. If the device shows infinity (one on the screen), then the coil is broken.

It is important to understand that the posistor is “live” only if it is cold. If you just checked the relay and it gets hot, let it cool for 15-20 minutes before checking again, otherwise the resistance readings will be incorrect.

Table of normal resistance values

For ease of diagnosis, we provide approximate resistance values ​​for various types of compressors. Remember that the exact parameters may vary depending on the manufacturer and model of the engine.

If your measurements differ radically from the data given in the table, this is a sure sign that starting relay has failed. For example, if the resistance of the starting winding shows zero, it means that there is a short circuit inside the posistor and the engine will not be able to start.

It is also worth checking the resistance between any contact and the metal housing of the relay or compressor. In good condition, the device should show infinity. The presence of any resistance indicates an insulation breakdown, which is dangerous for operation.

Typical faults and their symptoms

Understanding the symptoms helps to quickly diagnose the problem even before opening the back panel. Most often, users are faced with a situation where the refrigerator hums for 5-10 seconds, then a click is heard and the motor stops. After a few minutes the cycle repeats. This is a classic sign that the starting winding is not receiving an impulse to start.

Another common case is that the compressor does not make any sounds at all, although the light inside the chamber is on. This may indicate a burnt-out thermal protection or a complete open circuit in the relay. Sometimes the relay “sticks” in the closed state, due to which the starting winding is constantly energized, which leads to overheating and humming of the motor.

If you notice that the relay body gets very hot during operation (this can be checked by gently touching it while the motor is running), this indicates poor contact or an internal malfunction. In such cases, replacement of the part is necessary as soon as possible.

Replacement and installation of a new relay

After you are convinced that the old part is faulty, you need to purchase an analogue. Relays are selected according to the compressor power (indicated on the nameplate, for example, 1/8 HP, 1/6 HP) and the type of refrigerant. It is also important that the connection diagram and the location of the contacts match.

Installation of a new element is carried out in the reverse order of dismantling. Push the relay onto the three pins of the compressor as far as it will go. Make sure it fits snugly and doesn't wobble. Connect the wires to the appropriate terminals, following the color markings or photographs taken earlier.

After assembly, do not rush to close the back cover. Plug in the refrigerator and listen. The launch should be confident, without prolonged buzzing and repeated clicks. Let the unit operate for 15–20 minutes, periodically checking the temperature of the relay housing - it may warm up slightly, but should not become hot.

⚠️ Attention: If after replacing the relay the compressor continues to click and does not start, the problem may be in the motor itself (turn-to-turn short circuit) or insufficient voltage in the network. Continuing to try to start it is dangerous - this can completely damage the compressor.

In some cases, the contacts on the wires may not fit the new relay. Then you have to rearrange the block from the old device. Do this carefully, remembering which wire was connected where, since an error in connecting the starting and operating windings will lead to instantaneous combustion of the new part.

Frequently asked questions and answers (FAQ)